I enjoy hearing what people come up with. Here's a few of mine I've posted around here before

>Ability: Sprint
If the opponent is faster than this Pokemon when switching in, then this Pokemon will gain +2 Speed instantly

>Ability: Little Bud
Upon fainting, this Pokemon leaves behind a 1HP Substitute

>Ability: Frost Heave
The power of Ice-type moves is increased by 50% in Snow (Hail?)

>Ability: Double Dip
This Pokemon has a 50% chance at the end of every turn to recycle a consumed item of any type. This will not work if the item was destroyed or knocked off.

>Move: Snow Plow
>Ice, Physical, 70bp
The user drives a pile of snow into the target. If there are hazards on the user's side, this move clears the hazards and doubles in power.

>Move: Wave Fist
>Fighting, Special, 95bp
Punches an energy ball shaped like a fist at the target. This has a 20% chance of lowering the higher of the target's two defense stats. If the target Protects on this turn, this move will still deal 25% chip damage.

>Move: Glitter Bomb
>Fairy, Special, 60bp, 90%acc
Covers the target in glittering light, causing them to take double damage from Fairy type attacks until they switch out or are KO'd

>Move: Fluster
>Fairy, Status, 90%acc
Lowers the higher of the target's two attacking stats by -2

>Move: Blight
>Bug, Special, 90bp
Reskinned Ice Spinner but functions as a spread move that hits both opponents a la Heat Wave