Bob Long Torpedo, CP Regs, Centerflag, and AKA Sidewinder
I shoot a 2K5'd GZ, Excalibur, Viking, Texas Storm, Ripper, Ripper 2 and Ripper 3 Intimidators. I run a Halo or an Empire with a PMI Pure Energy Tank.
Small, incredibly consistent, easily adjustable.
This is the pinnacle of high performance regulators. Have Blue's analysis of regulators, their performance and recharge rates showed the AKA 2-Liter to be the best in the business. I've used two of them for the last year and a half to two years on my Intimidators and have had unsurpassed performance from them. I've never suffered shootdown and the recharge rates are amazing. The maintenance is incredibly easy (just a few drops of oil bled through every few cases of paint).
The 2-Liter Plus was an upgrade to the original 2-Liter and had a high and low output version for markers of different tempraments. The new 2-Liters eliminate this altogether and give you a 2nd spring so you can set it up yourself.
Other than the Sidewinder (also made by AKA), there are no regulators that even come close to matching the performance and reliability of the AKA 2-Liter. When you need a regulator for stable, consistent performance that's going to get you +/- 2 over a chrono, this is what you need.
It's the top product on the market today and fully justifies it's $95 price tag. Well worth the money.