Three of the EX Hard (or Expert Mode) skirmish missions award the player with a weapon if you can Kill the Enemy Ace AND complete the mission.

Unlockable	How to unlock
Anti-Tank Flamer Attachment	Kill the Enemy Ace in East Bank of Vasel EX Hard Skirmish. Near the center of the map and in the center of the Imperial's central force.
Anti-Tank Sniper Rifle	Kill the Enemy Ace in Marberry Shores EX Hard Skirmish. Ace is wearing Gallian attire in the small base separating the beach from the interior.
Imperial Anti-Tank Lance	Kill the Enemy Ace in Naggiar Plains EX Hard Skirmish. She's atop a sniper tower equipped with an AT Lance.