I'm partial to slings and nuts because they're light and cheap. I usually bring 20 m of 9/16 or 15 mm tape and a set of leaver nuts (stoppers, hexes, tri-cams, whatever, mixed). I usually only bring pins in the winter when I otherwise have a tool with, unless I know for sure I need pins. Add a few (1 for each rap station) quick links or leaver biners to ease pull downs. And bring rap gloves and a helmet! Rocks'll be a flyin', guaranteed!