This password list was posted to the pen-test mailing list at SecurityFocus.com. The origin of the list is purportedly a trainer from Foundstone, Inc. The post claims that this list works 80% of the time in penetrating a network (presumably, where a user account is known or guessed).
Password lists are abundant on the 'net, but most people don't refer to such lists and choose a weak password: they create one. Read Is your password on the worst offender list? for composing easily remembered, stronger passwords.
Another source of ongoing password pain are default passwords, the passwords that software and hardware manufacturers set before they ship products. The manufacturer intends and warns buyers to change these passwords, but they are often left unchanged. A fantastic list of default passwords is hosted at phenoelit-us.org. A list of default passwords for Oracle database is hosted at Pete Finnigan.
I am happy to provide attribution for the author of this list. Contact me if you know who composed it.
Begin List. 123456 1234567 12345678 123asdf Admin admin administrator asdf123 backup backupexec changeme clustadm cluster compaq default dell dmz domino exchadm exchange ftp gateway guest lotus money notes office oracle pass password password! password1 print qwerty replicate seagate secret sql sqlexec temp temp! temp123 test test! test123 tivoli veritas virus web www KKKKKKK End List.