I'm a gamer too and have tested several av's in the last months.
So i can speak for 4 solutions:
1.
Bullguard Internet Security -> Gamer Mode to deactivate background tasks ( you can see how many and wich processes are stopped during gaming). its a light av but in my opinion ugly interface and the protection depends on bitdefender signatures.
2.
Panda free -> very light....but no solid protection. he need a wingman like OSarmor or Syshardener.
3.
Eset Nod32 -> very light....my favourite AV for gaming. no impact, no delays...nothing...and strong protection
4.
AVG free -> light...and a little bit lighter with the avast tweaks of
@Evjl's Rain .
I was not very happy with Bitdefender AV paid ( heavy ram usage) and F-Secure IS ( little impact @gaming/work)