Originally Posted by Medion
FYI, Avira Premium also offers a game mode, though I've never tried it or looked for any tests on it. Avira itself doesn't take up many resources, and while that may still be an issue on an old single-core, it's not even an afterthought on my quad-core.
I just use Avast and disable realtime scanning. I leave on the network scanning though. Seems to do a good job at intercepting things before they are downloaded.