[Rapt0r9]

Really, you don't need very much.
(In order of Importance)

Safety Equipment (Always a must have. This includes a first aid kit and goggles.)
Wrench Set (You'll probably only need the 1/4, 3/8s, 7/16s, 1/2, and 9/16 wrenches)
Screw Driver Set
Drill (With assorted bits and spare battery)
Hacksaw
Electrical Crimper/Stripper/Cutter (It is better to have individual tools for each, but the all in one does work)
Pliers (Both standard and Needle-nose)
Allen Keys (Depends on what hardware you use, you may find these unnecessary)
Chain Breaker (Surprised nobody said this yet)
Hammer
Computer (If you have to, you could use the default code, but writing your own program is defiantly a good idea.)
Vise
Clamps (Vise grips are great)
Tap Set (Optional, but makes life easier)


I didn't mention any hardware, but stuff like assorted nuts and bolts are good to have around. Zip ties are invaluable as well as electrical tape (for insulating only). Also don't forget things like wire and crimps.

Out of all of that I could probably get by with just the first 6 items. It would take a while to get things done and working would be much harder than it needs to be, but it is doable.