I tried the few that are on here, and each had it's ups and downs. The closest I came to finding one that I liked was Dartho's:

https://vborg.vbsupport.ru/showthrea...ghlight=mobile

But (imo, of course, and no offense dartho) it's just... Ugly. There's so much CSS to customize to get it looking even remotely like your mail theme when in reality, all you really need are dark and light versions. It also maintains a lot of the extra goodies that make vB too big to render on slower connections - no matter how much I trimmed it, it was still a bear to download on a non-3G phone.

That's one of the big things that made me pony up the $125 for the WIForums product. It's optimized very well, loads in a flash and maintains just enough of the basics so that usability doesn't suffer. I wish the templates weren't encoded so that I could fiddle with them, but I can understand the author's thinking behind it because if that was the case it'd be pretty easy to reverse-engineer. It's really just well thought out and the fact that it's a completely different install than your regular forum is just the icing on the cake. Hit my site and login with guest/guest and check it out if you like.

(I hope this doesn't sound like advertising, feel free to edit this bit out mods if you see fit. I'm just passing on my experience with it.)

I'm sure that with enough time you could take the default vB theme and just go nuts cutting bits out of it, but it's just very time consuming and every time I'd have a go at it I wouldn't like what the end result was at all.