Here is the full list of all 42 REDSHOT achievements.
Pick up your Raygun
Pick up the Shotgun
Pick up the Assault Rifle
Pick up the Grenade Launcher
Pick up the Rocket Launcher
Pick up the Bow and Arrow
Pick up the Flamethrower
Pick up the Burst Gun
Pick up the Plasma Cannon
Pick up the Wave Rifle
Pick up the Legendary Sword
Defeat Lt. Wilkins
Defeat the Balrog on the bridge
Defeat Bobo
Defeat the Sand Worms
Defeat Naotabla
Defeat the Gunslinger
Take down a helicopter
Defeat Overgrowth
Defeat the Minotaur
Defeat the Leviathan
Defeat Southface
Defeat the King in Yellow
Find all 4 Power Cells
Increase Inventory space to maximum
Get the Wall Jump
Get the Double Jump
Locate the Artificial Language Intelligence Module
Get the Scuba Gear
Get the Jetpack
Wear a Hat
Reach 50 HP
Reach 50 stamina
Beat the game in under 4 hours
Beat the game without dying
Collect a total of 100,000 Gold
Beat the game on any difficulty
Aquire all Map Fragments
Win a game of Sportball
Aquire the Air Dodge ability
Complete the Bounceball Tournament
Complete New Game Plus