Each character in Grand Theft Auto 5 comes with a unique ability. Franklin, for example, can slow down time while driving. Nothing lasts forever, of course, which is why you should top off your character's ability with this special cheat.
On PS3, press X, X, Square, R1, L1, X, Right, Left, X
On Xbox 360, press A, A, X, RB, LB, A, Right, Left, A
For more, check out Prima's free GTA 5 guide.