I was trying to restore a database backup from one server onto another this morning, and despite the two having the same drive letters for data and logs, I ran into problems because the directory names were different. For a company that runs everything based on rules and standards to the point of excess, this is silly. So I'm making a quick list of SQL Server-related settings that I feel should be standardized across all servers in one's environment. It just makes things easier!
1) Directory structures
2) Default data and log locations
3) Drive letters, if possible
4) Build levels (Service Pack/hotfix)
5) Logins, although these may be different between Dev, QA, and Prod
6) Install locations - I have never found a valid reason to install SQL Server on the C: drive of a non-desktop, but I keep seeing it
I'm sure I'll add to this list as I come up with more obnoxiously un-standardized settings in our environment.