Closed end racheting wrenches. So freaking handy all over the bike, but especially on bolts where there's just not enough clearance to get even an adjustable wrench in there. One example are the bolts that attach the GEBE engine to the GEBE lower mount strap. With the closed end ratcheting wrenches you can make sure those bolts are nice and tight during your bike inspection without removing the wheel.
-Sam