Off the top of my head in no particular order. The return of GSP The addition of the 125 division The retirement of Fedor The fall of Miguel Torres (probably more significant for me than for MMA in general) Cormier wins SF HW tournament
Retirement of Fedor Introduction of 125 division in the UFC End of Strikeforce Bellator on Spike Cain winning the HW belt Jones dominating Anderson dominating GSP comeback title defense
Fedor and Randy retiring, injuries, women's and lighterweight mma making the move to the UFC, Strikeforce folding.