Here is the full list of all 70 Happy Room achievements.
Master of elemental weapons
Master of miscellaneous weapons
Master of cold weapons
Kill dummy with a fish
Complete all 97 dungeon achievements
Kill dummy with a saw
Kill dummy with a static mace
Kill dummy with a goblin
Kill dummy with a minigun
Kill dummy with a pitchfork
Kill dummy with a bomb
Kill dummy with a crossbow
Kill dummy with a guillotine
Master of fire guns
Master of explosion weapons
Kill dummy with a magic wand
Kill dummy with a sheep
Kill dummy with a spring
Master of all weapons
Kill dummy with a tesla
Kill dummy with a hay
Complete 48 dungeon achievements
Get all 120 achievements
Get all fatalities
Kill dummy with a jumper
Kill dummy with a gravity gun
Kill dumy with an acid gun
Kill dummy with a laser
Kill dummy with a monster
Kill dummy with a mace
Kill dummy with a deathray 3000
Throw dummy for 50 meters to the right
Throw dummy for 50 meters to the left
Reach the Moon
Kill dummy with a spikes
Kill dummy with an axe
Kill dummy with a stake
Kill dummy with a plasma gun
Throw dummy for 50 in the air
Hit a bird
Kill dummy with a rocket launcher
Kill dumym with a ice gun
Kill dummy with a mine
Deal 20000 damage in sandbox
Deal 30000 damage in sandbox
Kill dummy with a disco ray
Get 60 achievements
Kill dummy with a firegun
Kill dummy with a black hole
Kill dummy with a piranha
Kill dummy with a wall
Kill dummy with a wheel
Kill dummy with a grenade launcher
Kill dummy with a shotgun
Kill dummy with a shuriken
Complete all 76 armory achievements
Explode a mine
Kill dummy with a lightning
Kill dummy with a big rocket
Kill dummy with a spider
Kill dummy with a dragon
Kill dummy
Complete 38 armory achievements
Complete tutorial
Complete the first achievement