and the most underrated weapon in there is the splicer. i don't see many splicer users in the matches, but all you gotta do is throw a whole bunch at any angle off the walls, and you'll find them hitting guys you didn't even know were there :D
in big firefights, the splicer can net you a whole bunch of kills (though they are rather cheap)
i'm a bit sad that the power of the auger was lessened in this iteration, though it's still massive in the hands of a skilled shooter.
much fewer people still use the rossmore shotgun, but i've found that it's pretty useful when baiting overzealous dudes around a corner.
but by far my favorite has to be the marksman semi-sniper rifle.
anyway i really like the game. sorry for my overflowing affection :P