Pulse Rifle was one of those weapons that I found to be totally useless until I put a lot of nodes into it, and then it really kicked ass. Likewise, I wasn't a big fan of the Force Gun, Contact Beam, or Flamethrower until I dropped a lot of power nodes into them. I think the only weapons I really found "useful" right from the get-go were the Plasma Cutter, Line Gun, and Ripper.