Depends on where I"m riding, how long I'm planning to ride, and how far I'd have to walk out if I had a problem. I'll occassionally go for a ride without any tools, pump, or patch kit...but the farthest I'd have to walk out at those places would be a few miles.
On anything else, patch kit, spare tube, mini pump, multi tool (with chain tool...gotta have a chain tool).