Here is the full list of all 12 Alien Shooter trophies - there are 7 bronze, 4 silver and 1 gold.
Find the secret area
Complete a level without taking damage
Buy all character improvements, drone and night vision goggles
Use all forms of weaponry
Kill at least one monster of every type
Survive 5 minutes in Survival mode
Complete the first episode on any difficulty
Complete the first episode on maximum difficulty
Kill 1,000,000 monsters
Survive 5 minutes in Survival mode using pistols only
Survive 15 minutes in Survival mode
Complete the first episode without dying once