My MSDN keys that are just sitting there unused.
Win7 Pro key works for both x86 and x64 they are not class independent i.e won't work on Home Premium, Ultimate, etc...
WinServer 2008 R2 and Home server 2008 same as above x86 and x64 i have 2 of each.
WinServer 2003 x86 2 of each also
I used the Office Key this morning to register a new install so that is gone.
If you have anymore questions feel free to ask.