By no means an unabridged list, but some items I haven't seen listed yet and we found useful.
Set of numbered bits.
Reamers are great, as long as the bolts going through the holes are the correct size. On more than one occasion (read many times) we found that a bolt was .0008" (or even less) larger than the reamed hole. This cost us MANY hours until we got smart and got a numbered drill bit set.
Pneumatic Riveter
Pulling stainless steel rivets w/a hand riveter is a lot of no fun.
6" Digital Calipers
IR Thermometer
Not required, but much faster and easier for calibrating iron and often is on sale at Harbor Freight for $30