The following abilities can be obtained on weapon attachments.

Bayonet: Increases melee damage.
Boominator: Increases grenade damage.
Fast Learner: Bonus experience from kills.
Foregrip: Increases stability.
Harden Up: Improves maximum shields.
Higher Bullet Speed: Faster bullets to improve long-range performance.
Higher Damage: Increases base damage of weapon.
Improved Accuracy: Increases accuracy of weapon.
Increased Magazine Size: Holds more bullets.
Oxygenator: Damaging enemies will restore oxygen.
Piercing Rounds: Chance to penetrate enemy shields.
Punisher: Increased critical hit damage.
Reload Speed: Lowers the time required to reload.
Safeguard: Restores some shield capacity with each kill.
Serenity: Reduces oxygen consumption rate.
Wild: Creates a wider spray of bullets.