Wanted to add here the Walbro "W" tool and the Zama "Z" tool for setting metering lever heights in carbs.
A leather punch, X-acto knife, and a roll of fiber rubber gasket material and you'll be able to make your own gaskets.
A decent size zip tie cut at a 45º angle works well to clean bar grooves.
A adjustable air gap spark tester. This lets you test how strong an ignition coil is. A coil may be able to spark a plug in open air held against the block, but not have enough power to spark the plug under compression.
Tube of Permatex 518 anerobic sealant. Cures in the absence of air. Works very good for sealing metal on metal surfaces, like clamshell engines or cylinder/base surfaces on the larger engines. This same stuff is used to seal crankcase halves of 2 stroke outboards, all the way up to the large V-6 engines.
Having a roll or at least a couple feet of each common size of tygon fuel line is handy too.