Good quality hex drivers, and I mean GOOD quality
Good quality soldering iron (Haako makes great ones)
Dremel tool with cut off bits, sanding bits, and every other bit you can think of. I use my Dremel all the time.
Taps and dies for the screws you have on your kit
Extra bearing kits (Avid and Schelle sell them for a great price)
Screw extractor

If you are racing:
pit mat
pit light
tire cleaning station (if indoors)