[Switchblade]

I consider CJ Xtreme to be W's final form. Gold Xtreme I look at as being more like Kiva's weird bird thingy form. Besides, Shotaro and Philip couldn't use it at will like regular Extreme.

OOO's final form is PuToTyra. It fulfills every single criteria for being one, including having potential drawbacks, which only Kuuga and Blade have really done a lot with before. I really can't understand how anyone could not see this as the final form.

Also, I'd argue that Climax form is more of Den-O's final form than Liner, although the show itself was always kind of vague on this. Climax seemed generally more powerful, though, especially when it got upgraded with Sieg.