Another difficulty is how your team builds the robot. Do you have parts custom made for you by a local fab shop, or is most of the manufacturing done in-house?
Either way, I'd load up on tools and hardware. Determine what type of connectors you'll use (1/4-20, 10-32, 10-24, rivets, etc.) and get a bunch of that. Also tools specific to your connector. AndyMark sells packs of individual tools -
just the ones you need, not a big huge full set like at the home improvement stores. (Tip: put colored electrical tape around tool handles so you can easily identify by color)
Also prototyping materials are always nice. Plywood, 2x4s, etc. Stash big, empty cardboard boxes - they come in handy.