Well BanCandy is legit, and will ban a cheater.
Steps you need to perform:
1) Start Recording the Killcam and current play of the cheater; as much as possible – remember, you need good solid evidence here. If you do not want to use the in game recorder, you can use Fraps or any other similar program.
2) Capture the Steam ID of the cheater
a) Shift+Tab while in game
b) Click on "Current Game" and find name of the cheater (Note: the name displayed may differ from the name the cheater is using in game – you may need to view the Profile of a name that does not match up with the names of the players currently in game to see the Aliases they use or have used).
c) Copy the URL or make a note of the Steam ID
3) Upload the video to YouTube (you will need a YouTube account for this) or give her your Steam ID and direct her to your Vault. Name the game so she can identify it.
4) Copy the URL of the video on YouTube and the URL to the cheaters Steam ID Profile and/or your Steam ID.
Here is the Form for reporting- http://www.reddit.com/message/compose/
BanCandy's Reddit: http://www.reddit.com/user/bancandy - she will take it from there (she is a current IW Developer).
I have 2 videos in my vault with 3 cheaters I am about to link BanCandy too. This is no joke, and PC is as good as any platform. Don't waste her time sending BS complaints with sketchy evidence.
ALSO, link any new cheats, hacks, sites, etc. to her site.
Do your part and let's take back the neighborhood
Also, be sure to get their Steam ID so there is absolutely no question about who this person is. Shift+Tab while you are in game. Click on the person's name in Current Game (remember, their name in game may actually differ from the one shown so you may have to click on their profile to see what aliases they use or have used).