I don't know about the best PvP template... But the most overpowered right now is the Myst Mage. Basically take a necro mage and swtich the SS and Necro with Myst and Focus (focus is eval for myst). You can even put inscribe on the mage too instead of med since focus gives you some good med ability.
There is a patch coming very soon though which will alter up the PvP scene at least a little bit. Pure mages are going to get some love with as serious SDI increase, chiv is getting love (and hate, depending on your point of view) and the timer on apples is increasing significantly. Also, they're trying to get poisoning back into the game, but I haven't really rocked TC1 too much to see how everything is working out.
The SA expansion has lots of cool stuff to it, but the biggest change is imbuing. The suits and weapons that you can make today are just sick! If you want to pvp, you need to have a maxed out suit cause everyone you're playing against definately does. I know its tough to get started with imbuing and all that, if you need/want some help with it, PM me and I'll see what I can for ya.
The PvP community here is pretty active right now. Faction wise, we have the "new" COM guys that recently started fighting here on chessy again. I can't remember their guild name cause whenever I'm fighting them I'm at least somewhat tipsy and by morning I don't recall the name. Oh well.
TB has two opposing sides in their faction, EMP and UHOH (I'm pretty sure UHOH has at least one other side guild, but I'm pretty sure their friends). Lastly, MvP is still sporting some players in the MIN faction, but they're a shadow of their former zerg self and lost their core good players. However, they have strong backing from the non faction OATH guild which is huge. TKO runs around fel too, though I haven't seen them much recently, but maybe I just haven't run into them, I dunno. You'll see GS (still) hogging the guard zone at yew gate with rediculous tactics that are no fun. ACT will fight, but if they're not spawning, they generally hang out at the gate.
Those are most of the actual PvPing guilds, of course there are others who run around and spawn, but most of those try to avoid the fight rather than find the fight.