The best, in my humble opinion...

MY FAV GAME AT THE MOMENT IS.......

COUNTER-STRIKE
In case u havent heard of counter-strike(and u call ure self a gamer) it is a very good game pitting terrorists against counter-terrorists, it is an entirly online game that puts u in various differnet scenarious like:
Planting/defusing a bomb
Escorting/assasinating a vip
Protecting/rescueing hostages

I'll be sure to include lots of screenshots so you get a good sense of the game.

Tips and Cheats

Seeing as this is an online game cheating would only ruin the fun.....so here r a few tips that I hope will keep u alive just that little bit longer:
Crouching: This is a must if u want 2 be more accurate with a weapon...crouching greatly improves accuracy.
Jumping(bunny hopping): This will greatly decrease accuracy but will help in avoiding enemy fire. Best used when rounding corners.