The following abilities can be found on shields.

Absorption: Chance to absorb bullets and add them to your inventory.
Adaptive: Adapts to damage taken, increasing elemental resistance to that element as well as your maximum health.
Amplify: When fully charged, it causes your next shot to do increased damage at the expense of some shield capacity.
Booster: May spawn packs of shield energy when damaged that that can be picked up to restore your capacity.
Maylay: Improves melee damage after shield capacity is gone.
Nova: Explodes when your shield capacity is gone, dealing elemental damage to nearby targets.
Spike: Damages enemies that use melee attacks against you.
Turtle: Decreases health capacity for higher shield capacity.