Rain Sweeper Dialga
Dialga @ Leftovers
128 HP/ 252 SpA/ 128 SpD
Thunder- This is his most versatile move on this set. He can use it to hit a lot in Ubers with super and normal effective damage. With so many bulky rain stall/sweepers, he can punch holes in most teams with this amazing offensive attack.
Ice Beam- Thus his BoltBeam set is completed leaving very little able to resist him. He will now be able to hit almost everything super-effectively leaving very little in his wake.
Aura Sphere- With Aura Sphere, Dialga can hit everything (Excluding Shedinja, but who uses shedinja in Ubers) with at least normal effective damage. It also minimizes any chance of having other Steel types swtiching in on him.
Now adding a Dragon type attack in here would only allowing him to hit an extra 3 Pokemon super-effectively so I chose something else.
Earth Power- This added onto the set allows him to hit another 102 Pokemon super-effectively. Think about that an extra 102! Plus adding this move on allows him to have the best type coverage I have ever found!!! (Check it out, you might want to use this coverage)
So I think this set is uberly overprotective of ones-self. It can hit all of its checks exceptionall hard, and he also hase the bulk to take a few major hits. Plus, his monstrous SpA stat allows him to OHKO almost anything he is faced against!