Goozex because it's a good site, but truly the forums= hella mount of laughter (maf) and really good community thats pretty mature, quick to get games to, i have more than 15 games released since october that im first in line for just waiting on hold till i get to a point till i want the game seeing as i've played most of the ones im interested in. Plus if you can't afford $1 to trade maybe you shouldn't be playing videogames.
Secondly GameTZ. I do like some f the deals and oppurtunities, but what i do hate is there is a high amount of immature/ mentally slow people that are full of themselves and think they are the "shizznit" and their stuff is worth 2x as much. If you want proof of the immaturatetly level read through these pages and see people that just troll and bash other sites for no real reason.
TGN and sayswap i haven't tried yet, but no doubtly will and it will have their own god features and problems like every other site (goozex included).
Also, CAG needs to hurry up with its trading section because im sure i will be addicted to it like crack.