Patch kit
tire irons
multi-tool (hex and screwdrivers)
CO2 inflator
spoke wrench
Park combo-8/9/10mm wrench w/bottle cap opener
pair of nitrile gloves
Couple alcohol wipes for tube patching
razor blade (in the patch kit)
A thin rubber advertisement mat. I think it was a giveaway drink coaster. It's flexible and tough, so I have this for any sidewall mishaps.

And a mini-pump mounted to each bike.