On my commuter, I have:
a mini pump
patch kit
tire levers
spare tube
multi tool

On my "go fast" bike, I carry:
Co2 with 3 cartridges
patch kit
tire levers
multi tool

I always take my cell phone with me in case something catastrophic happens. Once, on a training ride, I had a chain explode on me, which also trashed my rear derailleur. Cell phone to the rescue and my son got in my truck and came and got me. In my 26 years of riding, that's the only time I had a chain fail me.