My combo is the Park Tool MT-1 multi-tool and the Park Tool CT-5 chain tool. Light, durable, cheap and compact. Oh, and a tire lever.

Here's the full set of stuff I take on a typical short-to-medium road ride, by the way. For longer rides I might take a second tube and a second CO2 cartridge. I don't bother taking a spoke wrench, since I don't have problems in that area, but this kit is enough to tear the bike down as far as the headset/BB cups.