Recently, I heard a song that I had forgotten for a long time:
Bolt Thrower - "No Guts, No Glory"
This is one of those songs that immediately reminds me of where and when I first heard it (on a CD I bought in Berlin on my 18th birthday, if you must know!).
This is, hands down, my favourite heavy metal/power metal/battle metal/whatever, song of all time, and one listen to it conjures up all manner of memories, flooding through my mind like some kind of time-river. They just don't make music like this any more.