So, this is one I have been using lately and it works really well. However, it requires sun support.
Shiftry @ Focus Sash
EVs: 252 Sat/ 252 Spe/ 4 Atk
- Dark Pulse
- Nature Power
This set works best as a late game sweeper or a wall breaker. Focus Sash ensures at least one Growth, that in the sun give 2x for both Atk and Sat. Solarbeam is just ridiculously powerful STAB, so is Dark Pulse. Nature Power becomes Earthquake in competitive matches, providing some excellent coverage. The Nature don't weaken any attack, and the EVs gives great power. There are some problems though.
This guy eats sweepers and scarfers for his afternoon tea, sporting an impressive 568 Speed stat in the sun, outspeeding almost everything unboosted. But he need Sun Support, or he is rendered almost useless. Another major problem is Priority moves, but I haven't had a lot of troubles with them. Entry Hazards also prevent the Sash+Growth combo, making his offensive powers decrease drastically.
Overall, I really like this set, and I hope you might consider this guy for your team!