Giro: Got to be Tre Cime, the final decisive stage with Nibali riding in solo in the snow to take the stage and overall win. That was just an epic scene. Special mention to stage 7 and 3 as well.
Tour: Annecy, loved watching Quintana attack and ride in solo for not only the stage win but also the KOM and 2nd on GC. Alpe d'Huez a close second, and also really enjoyed the winds on stage 13.
Vuelta: No contest, Angliru takes it easy. Tony Martin on stage 6, and Barguil on 16 were also really good.
For favorite of all, I'd have to say Angliru. Was great to watch Elissonde soloing in to the stage win, while at the same guy Nibali delivered attack after attack to try to break away. Plus the situation of the top 2 being separated by only 3 seconds added to the excitement. Tre Cime a close second, simply because of the scene at the top.