I wonder what I'm thinking of? Google, Google, Google
ETA: Hmmm. It might be the Vea I was thinking of after all. This is from the Johnson Creek website.
Can I Use Other tanks Or Cartomizers On My Vea® Battery?
Many cartomizers will fit on our Vea® batteries as they are a 510 threading style, which is the most popular threading style. Although they may fit, we cannot guarantee that they will work effectively or for that matter at all. Additionally, the Vea® batteries do not have outer eGo threads. Any cartomizer or tank that is not our Vea® branded cartomizer/Canteen™ you will have to try at your own risk as the batteries cannot be warrantied against failure if another product is used in conjunction with it. If you are going to try different cartomizers with the Vea®; batteries, check with the manufacturer for further information on specifics of their cartomizer to ensure they are compatible with 3.0 +/- 0.2 volt batteries.
Dang those are weak batteries.
Yeah, Vea is an oddity.
Another one is Blu--it's 510 threaded, so you can use any 510 threaded atty, but you can't use 510/eGo chargers because of reverse polarity.
There was another eGo style battery on the market, briefly, that had reverse polarity, but it didn't last very long at all.