For use in a Doubles Sun team:
Aurorus @ Assault Vest
EVs: 252 HP / 252 Atk / 4 SpD
Modest / Calm Nature
- Hyper Voice
- Earth Power
- Calm Mind / Rock Polish / Thunderbolt / HP Grass
Aurorus seems an unlikely choice for a Sun team. Anyone who watched its episode in the XY series will tell you it doesn't fare well in warm weather. However, Sun teams are often stopped dead by Dragon-types, who resist Fire-typed moves and Solarbeam. There are better choices for a Sun team dragon-killer (Mamoswine for example), but I personally like Aurorus more so I thought I'd give it a shot.
Hyper Voice (now Ice-type thanks to Refrigerate) is your dragon-killing move. It also covers two of Aurorus's weaknesses, Ground and Grass. It hits both opponents (or those near you in triples) for special STAB damage, with 90 base power, 100% accuracy, and without hurting your partner. A much better choice than Ice Beam.
Earth Power covers two other weaknesses, Rock and Steel, as well as covering Fire, which is a huge threat to any Grass-types on your team (especially with the Sun damage boost). Special move, 90 base power, 100% accuracy.
Psychic covers Aurorus's main weakness: Fighting-type. For what it's worth, it also covers Poison-types (who threaten Grass-types on Sun teams) that Earth Power doesn't affect, such as Crobat, Weezing, and Gengar. Special move, 90 base power, 100% accuracy.
This final move slot is up to you. If you manage to breed HP Grass, use it, as it covers Ground, Rock, and Water weaknesses. Thunderbolt works well if you want Water-type coverage. Calm Mind ups Special Attack and Special Defense, and Rock Polish doubles Speed. I use Rock Polish in order to have a speed advantage over slower enemies with type-advantageous moves.
Water, If you chose Calm Mind or Rock Polish, then remains the only non-covered weakness, which is negated by the Sun, and also covered by Solarbeam, which should be in no short supply on your Sun team.