When is it a good idea to force garbage collection?

So I was reading a question about forcing the C# garbage collector to run: http://ift.tt/1F0NfLQ.

Almost every single answer is the same: you can do it, but you shouldn't - except for some very rare cases. Sadly, nobody there elaborates on what are such cases.

Can you tell me on what sort of scenario is it actually a good/reasonable idea to force garbage collection?

I'm not asking for C# specific cases - but rather, all programing languages that have a garbage collector (I know that you can't force on all languages, like Java, but let's suppose you can).