I sometimes got accused of cheating when I used to online play, usually at Halo where I had an uncanny knack for headshots, and would usually wait until I had knocked someone's shield out before switching to a pistol for the coup de grace. I thought it was just a fun way for me to get someone, but I often got accused of cheating because I clearly couldn't be that good with a pistol.
My friends also occasionally accuse me of cheating when we system link play, but it's a lot more joking because they know that I have a thing for headshots, and we're all pretty evenly matched anyways. Also, the headshot thing comes in handy when we're all trying to get expert achievemtns on Left 4 Dead, so they put up with me scoring a few in MW2 or similar.