This is dumb, but I find myself using this a lot recently, and want to remember it. Some things I installed a long time ago put some assemblies in the GAC and I kept getting these gac'd references in my assemblies.

gacutil.exe /l 
| where {$_ -like '*nunit*'} 
|% {gacutil /u $_}

I really love the "|%" syntax. I wish C# had that: someCollection |% $_.SomeMethod.