Zhukov said:
Minimal killing (or zero killing, depends on how the game works) and no use of overpowered abilities.
Since you play as an assassin, zero killing isn't going to be an option if you actually want to finish the game.
I'm going to go for zero collateral. Guards, civvies, and so on will keep their throats, and most of my powers will therefore be based around traversing the area most easily without being spotted.
When a game goes the Deus Ex route and provides the possibility for a "pacifist" run, I feel like I have to try it out. If I want to go on a murder-spree, I can close my eyes and pop in a random disc from my library. But pacifist runs are unusual.