I'll bring the 30mm socket and breaker bar to do the belt tension. That's the only special tool I know of unless someone has an actual belt tension measuring tool (I just measure by gut feel). I presume someone has an 18mm socket in a standard kit. I have jack stands too.
Otherwise, I need electrical stuff that I have that I'll bring - Solder iron, solder, shrink wrap, connectors, etc.
If anyone needs an oil change, I can bring the socket for that too. I have the right size oil drain pan to fit under the SS while on the ground if anyone needs.