Bret Hart's constant weekly face / heel turns in '98 was annoying as fuck.
I loved Austin turning heel, pussifying him is what killed it though.
Actually, this heel turn made sense in a way. In the weeks leading up to the heel turn, much was made of his gang roots and how he needed a gang situation to stay focused, and that the Nation certainly was a gang. At CDIH, he fought all three Nation members (Faarooq, Savio, Crush) in a gauntlet match and was unable to win, causing the announcers to speculate he might have a new respect for Faarooq. Okay, so you might not have liked it, but at least WWE tried explaining a heel turn for a change.