I usually want:
Public Domain registrar account and password
Website (and website host if different) admin account
AD/Enterprise domain admin password
router /gateway and network switch passwords
Everything else i usually see as bonus to have but if I have at least these above items, then I can either gain access myself through one of the above, or can just "reset to factory" and start over, some times with that preferred. What do you guys add in the "must have" before the changes of departments/hands? Especially to make sure the company or myself doesn't get vandalized by unhappy previous IT and to make sure they get locked out from access.