I liked how Deus Ex had a lot of choice. I would play it like I would play any stealth game but I can't help using that move with the typhoon explosive system. (the one where adam has claymore ball bearings in his arms.) That move always left a smile on my face when you could clear a room if you were frustrated. It wasn't overpowering either.
Also in GRFS I like using the optic camo. It doesn't render you invisible- it's more like a futuristic ghillie suit to blend in anywhere- I mainly used it in foliage in MP and would hide along solid surfaces with it to good effect.