Here's a rotary tool (Dremel) sander that I just started using recently - it was in the '500 accessories box'. :-)

It's a mini-flap sander (60-80 grit) that's very handy for cleaning up edges of fiberglass tape, grinding rough spots where I've bonded a tie-down to the inside of the hull, grinding away epoxy drips that have been forgotten (past the scraper stage), prepping glass for bonding bulkheads, etc.

They are cheap from China on eBay.
Definitely wear safety glasses/goggles with something like this - I haven't had a flap sander disintegrate yet, but I'm careful to keep my face away from 'the line of fire'. :-)

Those Dremel knock-offs are so cheap (on sale) that I have several - it's handy to have one 'loaded up' with the right tool for the job.