patch kits (about $1.50)
tiny blinky lights (from $6-$9) - I found a great brand of these that are really little, attach with a little band, are really bright and totally cheap - if you are interested I can find out what the brand is.
Park MT-1 tools - the coolest bike tool I own - also small and inexpensive
Park tool bottle openers - don't know the price, but they are just cool