Double Team is annoying when it works, annoying when it doesn't. It's banned competitively, and even in-game, you're much better off just using a damaging move rather than spamming an evasion move.
Jolteon @ Life Orb/ Choice Scarf
Ability: Volt Absorb
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Nature: Modest/ Timid
- Volt Switch
- Shadow Ball
- Hidden Power Ice/ Signal Beam
Jolteon is best used as a full out attacker. Signal Beam is an option when you can't breed a Jolteon with Hidden Power Ice.
Ignore the EVs/ Nature/ items if you're using this Jolteon in-game.