Well I'm only about 1 1/2 years late, but it's always been my wish to main tank Naxx and full clear it. Even though we did it at 70 instead of 60, it was still quite fun. After a few weeks of preperation and planning with friends and such, we did it last night.
I was pissed I forgot to take SS of the 4 Horseman, but since I was tanking the last one in the far corner, I really didn't see much anyway.
Sapphiron's room is still the coolest (Pun) room in WoW so far.
The lich himself. Outgearing the place by almost two years made it just a zerg fest.
Finally, claiming his throne to myself made it all worth it.