I've tried a few fire builds for arenas that worked pretty well for pve also, but my favorite so far is
http://www.worldofwarcraft.com/info/classes/mage/talents.html?2150050302200140200000005523201030003105310000000000000000000000000 For Instance/raiding its basically a scorch build with imp scorch and fire power for decent sustained damage with points in arcane for a huge mana pool. For arenas theres loads and loads of added crit on top of ignite and chance to stun. It has the ability to be a 3 minute mage but it is not completely reliant on it. Combustion makes for even more crit and also gives you the opp for a PoM pyro crit. Oh and blastwave is just chronic for pvp. Even if you only have a 20% stand alone chance to crit, with this spec it will bump it up to around 30% leaving more room for stamina/spell damage/whatever else you might want.
The points in arcane can be switched around however you like, for pvp im personally a fan of imp arcane missiles, but most ppl put their points elsewhere.
Not sure if this is useful at all since this is one of my custom made non cookie cutter builds and is suited to my playing style, but if you can work with this build, its excellent for arenas or any other kind of pvp.