This is my favorite style of playing, mostly due to the fact that I am a terrible shot (in an FPS) or swordsman in this game and have to rely on surprise for half a chance. I've only played a short time, but have had some success finding an open path, getting behind folks (especially archers) and capping a flag by my self or with the few who catch up.
However, a secret assassin can't talk about his tactics, right? I'll say that I love the spiked mace. I'm still figuring out the game and on gen 3 haven't heir loomed much yet, but using unsuspecting things really helps.
It really helps to divide attention both for what you're after and what's after you. I've fallen for the ignoring-you-attacking-your-teammate-but-not-really feint too often.
Only on my 3rd gen, but am trying archery to throw a little change in. I've had a few successes of landing a few shots, being ignored, then slashing from behind with my cleaver.
High athletics, light armor, and quick weapons really help. Same with clever laddering.