Find a 'Shrine of Sparks' which is located near to some water and positioned in such a way that you can easily jump into it. Then if you activate the shrine and jump into the water you will get the 'High Voltage Treatment' Achievement.
Easy 'It Wasn't Me!' Achievement
If you activate a 'Shrine of Sparks' near a larger group of enemies some of them will eventually jump over and you will get the 'It Wasn't Me!' Achievement.
Easy 'Jumping Ahead of the Game' Achievement
You can get this Achievement easily by finding a Green Crystal (you will find the first one is somewhere in the middle of level 2) and then returning to the Single-Player 'Main' menu where upgrades are done and going to the right of the portal and paying a few goal to skip a level. Take the portal to level 2.
Easy 'The Cold Never Bothered Me Anyway' Achievement
You can get this Achievement easily by getting frozen by a penguin when you reach level 9 and then pressing 'Attack' until you break free.
Easy 'Weapon Unlocked: Bone Dagger!' Achievement
If you rush the boss with the 'Dwarf Turret' without using auto-attack you will get this Achievement easily.
New Game Plus
Complete the 10 levels of Normal Mode to gain access to New Game Plus.
Weapons
Meet the criteria to unlock these weapons. They may appear as weapons for newly generated characters.
Weapon
How to unlock
Bone Dagger
Complete 3 levels in Pacifist mode on a single run.
Easy 'High Voltage Treatment' ...