I think the black HISS is technically a POC vehicle, but I get your drift.
I really liked the look of the Polar Sharc when I saw it at the GI Joe con last year (it was in a display at Hasbro), but after seeing loose shots of it over on the Tank, it's not that impressive. Ice Storm isn't bad and would fit in with the new Adventure Team figures.
Other than the Volcano Viper, the rest of these kind of suck. Well, Leatherneck isn't terrible, but I don't think I'm tracking any of these down.
So far I've been lucky, I got hooked up on the RAM and Flight Pod and the former Walmart exclusive Shockwave/Night Viper 2-pack. I'd still love to snag a $15 VAMP, though. Actually, at this point I may have to settle for any VAMP I can get since it never hit retail here.