I tool that I didn't have, now I do, and I would replace immediately if lost.
Jawhorse. I used that thing again this week to help set up some new pallet racks. I would put five of them to use if I had them.
Second: Forklift. I spent so much time moving heavy stuff around and this makes it so much easier - you gotta learn to be careful with it, but when you do it works great.