Donkey Kong 64/Crystal Caves

You can use STVW on the wall below the igloo entrances to enter any of the rooms without playing the instruments. You can then walk out past the bars.
There are many places to use STVW, but the water level is too low for the glitch to be useful in many places.
Chunky can use the rock glitch to get out of bounds.
In Diddy's room with 8 enemies he must kill within a time limit, you can grab onto the center platform and pull yourself up without being noticed by the barrel enemies.
Lanky can use high jumps to enter the chimney of the ice castle without Baboon Balloon.
You can use the Baboon Balloon pad on the ice castle to get to Lanky's blueprint.
By damaging yourself to get invincibility and then rolling into one of the thinner parts of the ice maze, DK can glitch to the center. Video (#9)
Chunky can get into the small igloo with his Golden Banana by jumping and rolling. Unfortunately, there is no known way to get out. Video