1. Laser Rifles. I have 3 of them in my squad now - they can massacre from distance. One laser works not so good, but 3+ is a killer team. More lasers, more aliens won't even move close, they will be dead far before their plasma toys will be effective.
2. Flamers. Masters of close combat. Killing 3 aliens with one shot? Priceless. 12 TU and armored guy is mostly dead.
3. GL. If you are sneaky and creative, 3x shot can do miracles. Not to mention what GL does to multiply targets.
4. Bolter. 3x shot = dead body. Simple as that.
MG is not needed atm. Until we get 2x2 aliens, huge, bulky, armored ones using MG is like using nuke to kill a fly.
RL - meh.
Secondary, smaller weapons - I'm not using them.
And last but not least - wallhack - those thermo-vision-stuff is priceless.