I've heard of people filling them with soapy water and using a plasma cutter to cut the door while it is still filled with water. Also heard of dropping large quantities of dry ice into the tank to diplace the oxygen, making the tank safe to cut.
Team: Smitty's Real Pit BBQ
Superior SS-3 - Courtesy of Gainesville Jaycees and Superior Smokers
2 Custom Built Reverse Flow Stickburners
Weber 22.5" WSM
Weber 26.75" OTG
Weber Blue 2000 Stainless Performer