I've got wood.
HEH HEH HEH, HEH HEH HEH, HEH HEH HEH........He said "wood"
I have a Buck wood stove in my shp with a blower. It works great. Sucks if you want to heat the shop up quickly though. Im gonna install some kind of gas or propane heat to use for the times that I will only be there for an hour or two.