So many different ones depending on the job..
My most universal one I guess is an I phone and I pad.. used on all first time jobs or any that will be months in the completion.. I'll take many, many pictures of before, and during disassemble.. that have countless times saved me many hours or broken parts, nonworking final assembly.
Other then that.... 1//4 drive battery impact driver is a time saver on most my bike jobs.
And other then that, it is a large selection of tools at hand, that allow for the RIGHT tool to be selected for the task , or sub task at hand.. Not having to make do with the wrong tool... So yes I do need 10 different styles of metric wrenchs

Combo Long pattern
Combo Stubby pattern
Combo ratcheting box end long pattern
Combo ratcheting box end stubby pattern
Combo ratcheting Flex box end long pattern
Half moon
Flair nut
Off set box end
Crows foot
Tappet
And the list goes on