6. Swimming
Though Vice City brought us the ability to fly (properly) for the first time, players still couldn't swim until 2004. The GTA protagonists are tough nuts, and you certainly wouldn't want to get on the wrong side of any of them, but they're practically wimps when it comes to the wet stuff. One second in water, and that infamous "Wasted" screen pops up signalling your demise. GTA San Andreas changed all that and allowed its central character, Carl Johnson, to perform everyday actions for the first time in the series, such as climb over walls, up ladders and, yes, swim. Just as flying did, the ability to swim brought a new level of detail to the series, and Rockstar have stuck with it, because today, you can even drive submarines.