Well, the flamethrower(?) looked pretty badass from the latest Aliens trailer. At first I mistook it for a giant laser rifle (and was pretty disappointed when I discovered I was wrong, to be honest).
We aren't sure what kind of weapons the Marines will have yet, but consider that the setting is in the future so things could definitely be upgraded a little bit. And let's face it, a shotgun to the face will stop just about anything.
e: Oh shoot, I forgot to mention this. Has anybody noticed in the Imrogir 2009 updated Predator gameplay video that, when the Predator gets hit, his health bar gets segmented, but if he doesn't continue taking damage, it goes right back. It's as if he can take a bit of damage without actually getting hurt. It first happens when he fights the two Marines around the tree near the beginning, and once during his melee fight with the Aliens. Anybody noticed this, and if so, any thoughts?