Custom Sets that Work Very Well!

Here are some of mine, feel free to share yours!

This isn't custom, but it is horribly underused
Kyurem-B @ Choice Scarf
EVs: 252 Atk / 252 Def / 252 Spe
Nature: Adamant
- Outrage
- Fusion Bolt
- Earth Power
- Ice Beam

Works very well as a late game one man clean up crew, I'd say he finishes my opponent about 90% of games. The only move here that you will really ever need is outrage, but the others are good fillers. If your opponent is left without a steel type, or a scarfed pokemon, the game is over for them.

My Custom Gengar
Gengar @ Life Orb
EVs: 4 Hp / 252 SpAtk / 252 Spe
Nature: Timid
- Substitute
- Shadow Ball
- Giga Drain
- HP [Fire]

Always used as my lead, allows me to scout my opponent and make an excellent switch in, as well as having counters to most common leads (GG scizor, ferrothorn, politoed, etc.). Pretty much a beast set, and Giga Drain allows me to heal off sub+life orb damage, making this gengar last far longer that most.

Now it's time to share your own ideas! What custom sets have worked very well for you? (Provide justification)