I need all the help I can get on hills, so I like to keep the weight down.
1 tube wrapped in small rag, patch kit, 3 plastic tire irons and a frame pump.
Only time I carry tools is if I am experimenting with some adjustment(s). As CC noted, multi tools are too heavy, the proper hex wrenches will suffice. Most multi tools include about a pound of tools that don't even fit your particular bike.