Terminator Squad
Terminators are the iconic Space Marine elites. They have the excellent veteran statline, a 2+/5++ save, and carry a storm bolter and power fist. The squad can take an assault cannon, cyclone missile launcher, or heavy flamer for every five models in the squad. The assault cannon adds to the squad’s anti-infantry firepower while the cyclone gives it some flexibility by adding anti-tank firepower. The heavy flamer is generally not a good choice, as standard Terminators are not really assault troops. They don’t have the speed to use such a short ranged weapon, and they will be left in a poor position if they ever get the chance to fire it. Beyond this, any model can take a chainfist. I’d suggest at least one to give the squad the ability to carve up heavy vehicles or walkers. It’s a great addition for a few points.
Terminators suffer from being too well armed for every situation and paying a premium for it. Terminator armor is extremely durable but will fail against concentrated fire. Any AP2 weapons will cut through the squad depressingly easy, and they aren’t that uncommon, so be very wary of them. Terminators have respectable but not amazing shooting and assault abilities, but have difficulty leveraging both. You can think of them like well armed Tactical Marines. They’ll do pretty well in almost any situation, but not as well as real specialists.
I prefer to deploy Terminators by Deep Strike; this gives you the ability to place them where they can beat up on weaker squads without being exposed to anything with a lot of AP2 weaponry. Terminators can work well when used as bullies, quickly mopping up weaker enemy units that often can’t deal with such an overwhelming threat. If they come up against another squad with serious damage output, the Terminators will often lose the exchange. They can take a Land Raider as a dedicated transport, but I generally wouldn’t bother. If they’re in the transport, they’re not shooting, and that’s how Terminators will do most of their damage.
Terminator Assault Squad
Assault Terminators don’t suffer from the duality of standard Terminators. They are close-combat specialists with no shooting ability whatsoever. They come stock with a pair of lightning claws, excellent for tearing through lots of infantry. For a few extra points, each model can be armed with a thunder hammer and storm shield. This armament gives them the hitting power and durability to go toe to toe with the strongest combat units in the game. Their only real weakness is against hordes, which will eventually drag them down.
You can specialize the squad for fighting either numerous opponents or a few hard hitters by arming them exclusively with one type of weapon, but a mix gives the squad some flexibility. I generally take a squad full of thunder hammers and storm shields because I find that my Space Marines have difficulty dealing with monstrous creatures that reach assault.
Assault Terminators require some means of reaching the enemy. They come standard with Deep Strike, which will get them close to the enemy, particularly if you have a teleport homer on your forward squads. However, the best way to get them into assault with their desired target is to use an assault vehicle such as a Land Raider or Stormraven. I prefer the Land Raider as it can start moving into position on Turn 1 and my Stormraven always seems to die as soon as it drops into hover mode to deliver assault troops.
In conclusion, Assault Terminators fill a vital niche in the Space Marine codex. While Honor Guard are also an excellent assault unit, only Assault Terminators can reliably take on monstrous creatures and hard hitting characters.