Act 1: Den of Evil, 1 skillpoint
Act 2: Radamant, 1 skillpoint
Act 3: Golden Bird, 20 life
Act 3: Ruined Temple, 5 stats
Act 4: Izual, 2 skillpoints
Act 5: Anya, 10 resists
Act 5: Ancients, 1 level (usually)
Of course, Ancients is just a "speed up" in your levelling, as you can't use that to get past lvl 99
