Miter saw, seal kit for 3rd stall garage door to keep rain/snow out and my bottle opener on my workbench. I even use it to open my miller high life bottles.
Many 4 1/2" angle grinders with various attachments
oxy/acetylene torch
dry chop saw
welder
drill press
hand tools - screwdrivers-wrenches-socket sets, etc.
I have been thinking long and hard and honestly cannot come up with a "most used" tool or tools. I work on such a wide array of things I go from hand tools to air tools to machine tools to welding equipment. I can go a week and not grab the same tool twice.