saddle wedge. I keep a presta tube in there, some levers, an allen key set, a leatherman PSTII, and about 4-5 gel packs.
Yes, that bag is more heavily stuffed than the trunk of a geo metro on a family outing.
edit: oh and i forgot my cateye el110 led light, which I use as an emergency "legality" light for street when the batts on my niterider die.