Dialga Movesets

Dialga the Temporal Pokemon
It has the power to control time. It appears in Shinnoh-region Myths as an ancient deity. A Pokemon spoken of in legend. It is said time began moving when Dialga was born.

Mixed Attacking-Life Orb/Expert Belt-Quite/Mild Nature
Draco Meteor
Thunder
Fire Blast/Earth Power
Brick Break/Outrage

This moveset lets Dialga smash though walls. Giratina is KOed by Draco Meteor. Thunder takes care of Lugias and Kyogers. Fire Blast and Earth Power are good for Metagross, but the latter is better against other Dialgas. Blissey is destroyed by Brick Break, but Outrage get a super effective hit on Latias.

Expert Belt is preferred because this set is super effective against lots of Ubers.

Bulk Up-Leftovers/Adamant Orb-Careful Nature
Bulk Up
Outrage
Rest
Sleep-Talk/Earthquake

This moveset lets you take advantage of Dialga's awesome typing, decent Defense, and Attack. After a couple of Bulk Ups you can take hits with no problem, and Outrage becomes extremely powerful. Rest-Talk is also extremely effective in staying alive. On the other hand, Earthquake is nice to take out Metagoss, Dialga and Heatran.

Magnet Rise-Modest/Timid Nature-Adamant Orb/Life Orb
Magnet Rise
Draco Meteor/Dragon Pulse
Aura Sphere
Thunder

With Magnet Rise Dialga's only weakness is Fighting. Leaving its Ground weakness behind, floating Dialga can sweep. Draco Meteor causes you to switch often, so I suggest Dragon Pulse over it. Aura Sphere 2HKOs most Steels who switch in on you. Thunder is good in rain and takes out Kyoger and Lugia.

Special Choice-Modest/Timid Nature-Choice Specs/Scarf
Draco Meteor
Aura Sphere
Dragon Pulse
Thunder/Overheat

Draco Meteor with Specs will KO almost everything not Steel or Blissey. Aura Sphere conveniently takes care of Steels. Dragon Pulse is a reliable STAB that doesn't lower your stats. Thunder or Overheat can be used with either Kyoger or Groudon.

Physical Choice-Jolly/Adamant Nature-Choice Band/Scarf
Outrage
Earthquake
Overheat
Shadow Claw/Stone Edge

Outrage is a very powerful attack. This has the ability to one Hit KO Groudon and Palkia. Earthquake compliments it nicely KOing Heatran and other Steels. For the Steels that have left the ground, Overheat KOs them. Shadow Claw is a KO on the many Psychics in the Uber battling system. Stone Edge on the other hand, has a better chance to 2HKO Lugia, KOs Ho-oh, and hits Rayquaza harder.

Support-Modest Nature-Leftovers/Lum Berry
Thunder Wave/Toxic
Stealth Rock
Draco Meteor/Dragon Pulse
Flame Thrower/Thunder/Roar

This moveset takes advantage of Dialga's great defenses and typing. Thunder Wave lets you cripple all but two of the Ubers, and Toxic lets you hurt them all. Stealth Rock lets you support all of you teammates. The two Dragon moves are for either power or reliability. Flame Thrower lets you kill steels that switch in. Thunder also hits steels hard and Roar is for scouting purposes.