Boy do I know that about loosing the tool in your hand!
Lots that could be on a list, but just a few:
Good headlamp.
4 1/2" grinders (2; 1 for grinding, one w/wire wheel).
Mig welder (too easy to get it done).
Oxy-ace. torch (more for heating than cutting -- especially now that I have the plasma).
Battery drill and sliding bit holder (tube slides over the screw holding it straighter for you).
Radial arm saw (watch craigslist -- the one buy in tools you can't beat).
Decent table saw (yes, you can go too cheap here).
Sawzall (unless you use it all the time, buy a mid size model -- saves the arms).
Framing nail gun.
4+ way screwdriver (saves a lot of trips for small jobs).
Buckets and tool bags (I like to have tool bags/boxes for particular types of work: electrical, signal/coax/cat5, framing/building, etc; plus the do all buckets for the 'stuff' on a particular project).
Utility knife (saves my serrated pocket knife -- which I always have with me -- more often than my wallet)
Corded rubber ear plugs. They fit under everything.
Long arm floor jack.
25 or 30' tape measure.
6" triangle square.
Pencil.
Crescent wrenches (non-mechanic work).
Vice grips & chanellocks.
Large spring clamps (at less than $5 a bag, sure speeds up projects).
Cardboard: save those large sheets and throw them under your work. Over spray, spills, cheap creeper (especially in the cold), saves being sore (especially on concrete or asphalt), pull your tools out from under what you worked on when finished.
Kroil and a delivery bottle with a tube.
So many to mention!