Pure Energy Co2 tanks, Pure Energy steel nitro tanks.
Tippmann EM98C w/ way too many upgrades to list.
-Very quick recharge rate
-Backed by a great company
I haven't found any as of yet.
I bought the 68ci 3000psi with a Freeflow fiber wrapped bottle. This is the only nitro tank I've ever owned and this is the only brand nitro tank I'll ever buy. The recharge rate is not matched by anyone else and the quality and consistency of the regulator are fantastic. I can really rip with my ebolt 98 custom and this tank never lets me down. In a heated snake battle, I've never experienced a drop in velocity or accuracy. Also, I get about 900 shots off mine when using my lp kit and Palmer's stabilizer.
Darn good product. It's the only brand air tank worth buying.