In the Timbuk2 -

Bike stuff: Lock and cable, allen key set, adjustable head wrench, Gerber multi-tool as well. Spare rear blinky.

Non-bike - pack of pocket Kleenex, small first aid kit, spare shirt/jacket/layer for layering and weather changes, notebook, camera (SLR or digital depending), pens, Nalgene water bottle, and wallet.