A combination screwdriver
small adjustable wrench
5mm allen wrench - almost all allen screws on bikes (my bike at least) are 5mm
tube patch kit
Co2 inflater and cartridge
all of this fits in an old army ammo pouch that is attached to my sissy bar. Plus I always have my leatherman tool and cell phone on my belt. I used to have saddle bags for grocery and/or beer runs in which I would carry a small bottle of oil, but after switching seats I haven't gotten around to putting them back on.