Right now I'm using Duelist with Sniper and some Rifleman abilities. Works terrific in and outside interlock. And I have specials for all the states that can be caused inside interlock.
h4x, that's mah load =p. I think a lot of people are running some variations of this lately. On Kashira I've been running full sniper tree, basically the whole left side of rifleman, and down a ways into duelist for interlock situations.
Spindraft's currently been running knife chucker, full tree except for MKT, and down to combat enhancement. Ends up with a quite higher accuracy, he doesn't miss much on power attacks and a miss is exteremly rare on speed.
I've only recently returned amidst cr2 after a bit of a break, and a departing player was kind enough to give me her trees (I gave mine away last time i left =/), so i've been playing around w/ them a bit, but these two setups are my favorite so far.
Tried Fu-rate for a while too, fun for a bit but i dunno, i just get bored with doing constant interlock.
Gunman. I hate the class in its entirety but it's soooooo adaptable. T_T This is the only class that I can mix and match to meet any threat. Even MKT's. The damage potential is obscene as well. They use less IS than MA, are devistating in interlock and out, host a plethora of overpowered moves...and alot of people don't know how to use them correctly. They get old after awhile but it's by far the most powerful tree for solo acts. Maybe a little too powerful...
UtM kicks arse