Useful Things
Parts, tools, bits, potions, lubes, etc. to make life easier
Sealants, Threadlockers, etc.
Handy Sticks
I'm a big fan of Loctite-inna-stick especially for in the toolbox
Loctite 268 High Strength Stick 19g (1709314) - for things you absolutely don't want to come undone ever again
Loctite LB 8065 Copper Antiseize Stick 20g (525380) - for things you want to be able to undo later
Loctite 248 Medium Strength Threadlocking Stick (1709314) - for things you want to stay put but still get apart again
Loctite 561 Pipe Sealant Stick Low Strength 19g (540920) - for things you don't want to leak (574 below is better but not available in stick form)
General purpose workshop potions
General purpose sensor-safe silicone sealant - Loctite 598, or Dirko HT
Fuel safe sealant Loctite 574 multi-gasket sealant