For me, it differs for the game mode. Since I don't play multiplayer, I'm focusing on Single.

Best weapon = powered up fast blaster. Nukes everything in its path, drains bosses health super fast. It also travels pretty fast. Oh, and in SP, the missile weapons (seekers, TNT, RFs) suck most of the time because Fastfire does nil to them, and Pressing space rapidly tires quickly.

Whee, I bet I made several people in this topic ticked off by saying that. Oh yeah, and page claim.