So the self proclaimed Emperor's Finest decided to get stomped on by the Adeptus Titanicus - how do they keep from getting squashed into a fine paste in one turn?
Marine's usual strengths of T4, 3+ save are of little good when trying to take down a Titan. Most of the Titan's shooting attacks are S8 or more, and are all AP3 or lower. In assault it hits at S10, ignoring armour saves on 4+.
Marines can pack a whole lot of melta, but melta needs to get close to do its damage, and being near an exploding Titan is never fun.
So what to do? Well lets go through the Codex and look at each unit's viability as a titan-killer.
Commanders/Captains - Not a bad option overall, the Commander can use his orbital bombardment at range, or be equipped with a Thunderhammer and Storm Shield for survivability.
Cons: No big downsides, but no big plusses either. Not an overly cost effective choice.
Chaplains - Useful for buffing friendlies to maximise hits, but weak himself for killing power. Can get a Jump Pack or Terminator Armour to boost those potent units though.
Librarian - Has good potential, though it is highly dependant on power choice.
-Force Dome can be used to increase survivability somewhat (something's better than nothing!)
- Machine Curse can automatically put a glancing hit on a vehicle. While it won't knock off any structure points it has the potential to shut down movement and shooting. And a titan that isn't shooting is as good as dead.
- Might of the Ancients isn't a bad second choice giving the Librarian a pretty good chance with a fair number of attacks.
- Gate of Infinity can be used to rapidly redeploy a dead shooty unit right up close, though is somewhat unpredictable.
- Vortex of Doom should only be used if the Librarian is in Terminator Armour (making him Relentless), but isn't that hot.
Master of the Forge - Three Thunder Hammer + two power fist attacks on the charge (after shooing his combi-melta) makes the MotF a fairly solid contender to mix it up in an assault. Swapping out the harness for a Conversion Beamer isn't so bad - it has good strength at mid range and S10 at full range, something the Marine list lacks.
The 2+ save is good, giving protection from many Titan weapons, but the lack of an invulnerable save leaves him vulnerable to big blasts.
Terminators - One of the better options, but with a few glaring weaknesses. While they are expert at wrecking Titans up close (ten guys with Chainfists) their shooting is ineffectual. If you're counting on Rending from Assault Cannons and glances from Cyclones don't expect to see the big guy falling any time soon. They also suffer from either being slow (no assault after Deep Strike) or sitting in a vulnerable transport and getting stuck on foot.
Assault Terminators - Similar to their shooty brethren, but with improved survivability (TH/SS versions - but LC/LC is pointless against a Titan anyway). They suffer from the same weaknesses, and with the added problem of only being able to deal with infantry roadblocks by assaulting them.
Assualting is still a risky business as a Titan can Stomp. Stomping means the Titan can execute a single attack against any model in base to base contact. These hit on a 4+, ignore armour and are S10. Storm Shields give their handy 3++ save, but they're going to get hurt back pretty badly as everyone's at initiative 1.
However in multiples Terminator squads really shine. By this I mean three or four squads teleport down. There are two 'tactical' squads to gun down enemy defenders and screen for counter assault. Between these squads are TH/SS assault units. They simply run closer to their target and hope the other squads can hold off any nearby enemy infantry from assaulting them and tying them up in a mire of bodies.
Sternguard - Ten guys in a drop pod with combi-meltas and meltaguns. Add Vulkan to really make that Princeps cry. The drop pod's special guidance rules mean you can land in the tiniest gap without fear of mishap. The only thing is to make sure you have enough room to get out, get LoS, and get within 6" for those precious 2D6 pen rolls. Landing perfectly will do no good if you're to close and have to disembark on the far side of the pod so half your guys can't see, and the others are more than 6" away. Also keep in mind that you may potentially need to draw LoS upwards to avoid shooting through screening infantry.
Also bear in mind that the AP1 bonus does not exist on the Superheavy Damage Chart [edit: IT does as of IA:A2]. The only reason to take melta is to easily penetrate the armour. I can't help it if you roll all ones after that.
Don't expect them to live long after they land though, so don't bother with melta bombs or power fists.
Dreadnoughts - Similar to Terminators, but with the ability to take a multi-melta. Drop podding a MM dread can cause some serious havoc to a Titan. It gets the 2D6 penetration from 12" away, which is conveniently within the Titan's void feilds. They're not bad in assault either, hitting pretty hard (and before the Titan, which Terminators do not do).
The Ironclad can get a Chainfist, which is better than the Seismic Hammer (as the Hammer's +1 on damage charts doesn't transfer to the SH damage chart). It also has a meltagun, but is slow and vulnerable, a probelm of all Dreads. They also have the issue of being vulnerable to being tied down by a wave of cheap infantry. Imagine your horde of drop podding assault dreads getting swamped by squads of Penal Legionairres - they're stubbon and can potentially get Rending - those Dreads wouldn't be going anywhere anytime soon.
Dreads do have one very good use - equipping for long range fire and knocking down shields with missile and lascannon fire. Also the Imperial Armour 2 Mortis pattern with autocannons or missile launchers can pretty reliably take down void shields for not many points.
Techmarines - The Master of the Forge lite. A good add in for some face beating power, and pretty cost effective. Not bad, but only a foot option, so slow.
Tactical Squads - "Jack of all trades, master of none - but oft times better than a master of one." This is not one of those times. In shooting they are only going to be hitting with one decent weapon (two close up with a combi weapon), and in assault krak grenades do nothing, and a single melta bomb hitting on a 6 isn't great. The Sergeant can also take a power fist, but the Titan will promptly stomp him back. Not lookig good for the Sergeant.
Scouts - Mounting them in a Storm or on bikes and using them to bring Terminators via teleport homers is probably the most they can contribute to the fight.
Or they can hijack another titan before the battle, and eat the crews brains to learn how to pilot it and ride to victory [/obscure reference].
Assault Squads - Suffer from the weaknesses of the Tac squad, but do it faster. They are useful as a support unit to remove (or at least tie up) support units to allow heavy hitters like Terminators to move in.
Vanguard - If you feel like living dangerously they have alot of potential: They can assault after deep strike, can all get melta bombs (or Thunder Hammers if you feel like splashing the points around). They can also get storm shields for added survivability. This sort of unit will be around 800pts, but if it works it'd be great. After the initial assault they'll either be shot to pieces or swamped with crappy infantry to stop them having a second go.
Land Speeders - Deep strike - check. Two multi-meltas - check. Pretty cheap - check. Can't be locked in assault - check.
Can be made useless by a single glancing hit shaking, stunning or degunning it - also check.
One of the best units available for rapid Titan killing, the humble Land Speeder can pack a pair of multi meltas for under 100 pts. They can deep strike, which risky, gives them a great approach that is near unstoppable (for one turn at least). Their obvious weakness is AV10 and being crippled by any shaken or stunned results. It's almost preferrable to lose one of the meltas or be immobilised, so at least you can still shoot (the chances of the huge titan getting out of LoS of an immobilised speeder is pretty low.
Even without deep strike speeders will probably register a low threat initially, or at least survive through turbo-boosting. Should the enemy decide they need to be killed, your cheap speeders are taking fire that could well be sent elsewhere.
As it is an Apoc game, the decision is up to you wether to squadron the Speeders. Squadroning means you can ignore Shaken results, good for flying up a flank. However the proliferation of massive blasts could mean you suffer from the 'wound allocation' system more than normal.
Attack Bikes - Small cheap multi-meltas. They are superior to Speeders in that they can hide from the huge amounts of ordinance flying around the board to get to their target. They are slower and in some ways more vulnerable. A fairly good choice, but I wouldn't build a strategy around them.
Devestators - Though expensive and often put down due to expense, in Apoc they have their uses. With the larger table size their greater range becomes more aparrent, and being infantry (as opposed to a Predator Annihilator for example) they can sit in some secure terrain, immune to stunning, being irritating while the suckers... I mean glorious assault units... in the Land Raiders get blown to bits by StrD barrages.
- Four missile launchers can be used to hammer void sheilds and put holes in infantry screens. Fire enough kraks at the body and you could get some glances.
- Four lascannons can do the above, but also have a slightly better chance of getting hits on an un-shielded Titan.
Thunderfire - A very potent option, though not an obvious one. The key is using a Titan's strengths against itself. The Thunderfire boasts one of the longest ranges in the Marine arsenal, and has a very useful fire mode called Subterrranean. When you hit a Titan (not damage, just hit) if it wants to move it must move as if in difficult terrain (as it is a walker) and take a dangerous terrain test (as it is a vehicle). This can be used to effectively pin a Titan in place so it can't get out of LoS or away from an assault unit.
The Thunderfire can also chew up defending infantry pretty handily and is an easily overlooked piece of hardware.
Land Raiders - The standard Land Raider can do some damage to a Titan. Two lascannons (twin linked), an optional multi melta and filled with Terminators spell trouble no matter who you are. However they make nice juicy targets for any anti-tank gunner.
They are best used in multiples (much like Terminators) with standard models hanging back empty while assault troop laden Crusaders roll forward to disgourge their cargo. The Titan then has to choose to take out the assault troops and get whittled away by the lascannons, or kill teh long range fire but get a face full or chainfist.
And besides, if you're marines why wouldn't you field half a dozen Land Raiders?
Predator - A relatively cheap way to get massed lascannon fire, but a stunned result makes it useless. I'm more a fan of the Destructor for anti-infantry, bit others swear by Annihilators, so your mileage may vary.
Vindicator - While dead shooty it is a victim of short range and crap side armour. They need to get to point blank range to do any damage, and that's a pretty big ask. Better off using them to clear other things out of the way for other units.
Calgar - Expensive, and good at punching things, so a viable choice for your Titan destroying needs.
Sicarius - Nothing to benefit a titan killing mission apart from being able to give Tank Hunters to one unit.
Tigurius - A lack of Eternal Warrior and an invulnerable save (outside of Force Dome) makes him poentially less useful than a regular Librarian for his points.
Cassius - Not worth taking in my opinion.
Pedro - Stubborn isn't bad, but their are better ways to get it like...
Lysander - Eternal Warrior, terminator armour, TH/SS - this guy was made for ruining a Titan's day. The best character if you plan on a titan killing endeavour.
Shrike - Fleet is alright, but not fantastic. Ok, but there are better.
Vulkan - Twin linking all meltas, and making all thunder hammers master crafted. Bye bye titan.
Khaaaaaan!!! - Heh, Khan...
Legion of the Damned - They have some acurate deep striking, can fire after deep striking and have a good save. Not a bad unit to have in your list as a plan B for taking out a difficult target.