Successfully complete a party member's Loyalty mission to unlock their individuals skills for Shepard, alternate costumes, and increase the chance for surviving the suicide mission. Note: Complete the Advanced Training research upgrade for your ship to be able to select the skills.

Armor Piercing Ammo: Archangel's Loyalty mission.
Biotic Barrier: Jacob's Loyalty mission.
Dominate: Kill Samara during her Loyalty mission and have Morinth replace her.
Fortification: Grunt's Loyalty mission.
Geth Shield Boost: Legion's Loyalty mission.
Inferno Grenade: Zaeed's Loyalty mission.
Neural Shock: Mordin Solus's Loyalty mission.
Reave: Samara's Loyalty mission.
Shield Drain: Tali's Loyalty Mission.
Slam: Miranda's Loyalty mission.
Warp Ammo: Jack's Loyalty mission.