I'll start:

>Radioactive
Deals 1/16 max HP damage to all Pokemon on the field including this Pokemon. Grants this Pokemon immunity to Burn and Poison. Pokemon with the abilities Magic Guard and Overcoat ignore the damage from this ability (but Safety Goggles do nothing!).

>Sprint
When switching in, gives this Pokemon +1 Speed if the opposing Pokemon has a higher Speed stat

>Barricade
Prevents all other Pokemon on the field from switching out, including allies

>Hindrance
Prevents the opposing Pokemon from using moves that boost its Speed stat. If a move boosts other stats plus Speed (like Shell Smash), this ability will only block the Speed boost. This ability does not affect priority attacks or moves like Trick Room

>Neat Freak
Clears the field of all hazards upon switching in (auto-Defog)

>Evergreen
If this Pokemon takes direct damage and falls below 25% health, it will automatically heal back 30% of its HP. Can activate multiple times, even mid turn or during multi-hit moves

>Herbaceous
This Pokemon gains some of the properties of a Grass-type, gaining Grass STAB, a Grass resistance, and an immunity to powder moves

>Cesspool
This Pokemon absorbs Poison-type attacks as HP (i.e. Volt Absorb)

>Repulsive
If this Pokemon switches in, opposing Pokemon of the opposite gender will immediately receive -1 Att and -1 SpA

>Loudmouthed
Increases the power and accuracy of sound-based moves by 20%

>Double Dip
This Pokemon has a 50% chance to recycle its consumed hold item at the end of each turn. Does not affect Berries, but includes items like Weakness Policy, Focus Sash, Electric Seed, etc. Does not regenerate items removed by Thief, Knock Off, etc.

>Blustery
This Pokemon brings strong winds with it, causing a Tailwind immediately upon switching in

>Stone Skin
Reduces all stat decreases to just 1 level, including those that are self-inflicted (ex. Screech causes -1 Def, Shell Smash drops -1 Def/SpD)