SCPs
Safe
Safe class SCPs are well understood and safe if rules are followed. SCP 999 is a good example. It poses little threat and is easy to contain.
Some well known Safe SCPs are:
SCP 999
SCP 005
SCP 011
SCP 013
SCP 014
and SCP 131
Euclid
Euclid SCPs are not well understood and more dangerous than Safe class. SCP 096 is a good example. It is not well understood and poses a threat if left uncontained.
Some well known Euclid SCPs are:
SCP 096
SCP 049
SCP 173
SCP 079
SCP 073
and SCP 093
Keter
Keter SCPs cannot be understood and extremely dangerous if let uncontained. They are even more dangerous than Euclid class. They can result in an SK-Class End of the World Scenario. SCP 682 is a good example, it very hard to understand and can destroy everything if left uncontained.
Some well known Keter SCPs are:
SCP 682
SCP 058
SCP 035
SCP 076
SCP 106
and SCP 1048
There are thousands of other classifications but these are the main three, known as the SEK.