Jethro Tule 15mm wrench, a 17-in-1 Crank Bros Multitool and a pair of tire levers. The Jethro Tule is my keyring and stays in my pocket, the other two go under my seat with a spare tube and a patch kit. If I carry my bag I'll have a small pump too, otherwise I'll count on gas stations as I do all my biking in the city.