Although the pulse rifles look sweet
The pulse rifle rocks. The thing I like most about it that it has a very small stock, so a minifig wearing body armor can still shoulder it without having to hold it off center (which is an issue I have with many of the guns produced by Lego, especially the Star Wars blaster rifles). Of the Brickarms weapons I own, the pulse rifle is certainly my favorite.
As for the one I dislike the most, any of the weapons without a pistol grip qualify, since you can't ever have your figs aim them, just pose (which also why I was really disappointed in the brickwarriors steampunk rifle).