Here is the full list of all 11 Acorn Assault: Rodent Revolution achievements worth 1,000 gamerscore.
You defeated the Gate Keeper
You defeated the Tax Man
You horded 1000 acorns
You purchased 4 heal powerups in a single turn
You created a bomber
You purchased 4 defense powerups in a single turn
You created a wooden barrier
You purchased 4 powerups in a single turn
Defeat Marie Antoinutte in story mode
Defeat Marquis De Baguette in story mode
Defeat the King in story mode