I used to use a video renderer that allowed me to see people through walls and smoke but since I got my new video card I changed that to make it more "performing" and therefore I don't have that issue anymore.
Also, sometimes when in a server with, usually, close friends, I may use certain bugs (like the M16A4 30 semiauto 40mm sprinklers from the sky) to have fun for a few rounds.
In terms of anything permanent, I don't do that kind of thing... but some temporary things that I can't control I try and avoid, like the G36 sight not obscuring view because it's INVISIBLE, I used to use the G36 quite a bit until then, now I'm waiting for a fix, until then I'm trying not to use it just to be "fair".
I dunno if anyone thinks I DO cheat, but I'm nowhere near as good as Taque or the dukebot Ver.3.0 with speech recognition.
Although on the conversation of hitting someone at XXX range and killing them, I do it all the time! and without scopes usually. Half the time when I use a pistol it's all luck, I try and hip it while jumping down from god knows where and manage to either kill you or yell out "Shoot me! SHOOT ME!"
I remember once on LondonCity EAS map, I was riding the chopper and I had my robar scoped and looking to the left near the park area where the defenders go through to reach the main street. One dude was sniping down the street from there and I hit him while still moving and he accused me of cheating (I forget who). I just say it was a good and lucky shot. Just cuz I'm good with the blast cannon don't mean I gotta cheat, ya know?
)
That's the kind of passion we like to see in our soldiers. 
