Items I always carry that weigh next to nothing and pack easily - at least 4 bills of any denomination to serve as tire boots, (I've used 5 to get home from a big cut.) I also bring the allen wrenches specific to that bike. Usually a 6, always 5, 4, 3 and one bike has a 2.5. But I never carry this stuff in my pocket. That's tool bag stuff.
Ben