Beaufort Cipher, is a polyalphabetic substitution cipher that is similar to the Vigenère cipher, except that it enciphers characters in a slightly different manner.
Four-Square Cipher encrypts pairs of letters (like playfair), which makes it significantly stronger than substitution ciphers etc. since frequency analysis becomes much more difficult.
Vernam Cipher (also known as the one-time pad (OTP)) is an encryption technique that cannot be cracked, but requires the use of a one-time pre-shared key the same size as, or longer than, the message being sent.