Ruger Mk I. Once it's clear, remove magazine, pull down the little lever, pull out the bolt stop pin, and slide off the receiver, pull out the bolt. You might need a small "tool" to pull the lever down when new, but once broken in, a fingernail works fine. Ditto the receiver, a sharp blow from a non-marring hammer when new. But my MK I just need a rap from the palm of my hand.
Now some folks make a big deal about getting it back together. But, "IF" they read the instructions, it goes back together just a easily. Problem is they just don't spend the time to fully read the instructions.