- CO2 pump with a couple cartridges
- tire levers
- hex wrench multi-tool
- 15mm wrench for axle nuts
- spare tube
- patch kit

i don't bother with a chain tool and extra chain links. i've had a chain break on me only once in 5 years of daily bike commuting. that one time that it did happen, i just walked my bike over to the nearest el station and rode the train home with my bike. on my commute route, i'm always within a half mile walk of an el station.