For during build season, we have all the cutters, tools, and everything else you'd need in the shop. However, at competions, I sometimes need to slice a wire, a piece of tape, or rope, or cut something faster, so I just carry my lockblade. So far I've never had any trouble with it, but if a venue had an issue, I would be glad to take it out to a car in the lot, and not bring it inside.

As for a multi-tool, one of our members uses a leatherman with it's blade, but keeps it either inside the shop, or off campus. The school has never had a problem, even though the principal has come in with him using it.

A good strategy to find out about the upper limit that you can use is to go and ask the school admin's what they would let you carry/use for robotics, but keep in mind you need to tell them what you'll be using it for. This only really works if your team has a good impression on the admins though... good luck!