Changing corporate password
I've moved most of my password storage to 1Password app so that I don't need to mind the keychain when it makes more than one copy of a password. the benefit of that is I can have my passwords synced to iOS (and other OS) as well as save them periodically to a USB drive for disaster recovery.

Keychain doesn't do any of these as well as a tool made for managing passwords. As a bonus, I end up making much more secure passwords programmatically rather than typing them by hand.