Many Amiga tunes hold a fantastic hum-ability factor. After all, that's what the tunes were designed for - draw you towards the game and be as addictive as possible!
I've hummed many tunes over the years. Robocod, Super Cars II for some reason immediately spring to mind, as does Shadow of the Beast.
Rock N Roll had me humming that level one tune for ages as did the intro to Blood Money. The Settlers tune was stamped in my subconscious for days after I finished it in one sitting. Battle Squadron, Turrican series, Lotus 3 oh flippin heck the list is endless!
Yes, Amiga tunes definitely had high hum-ability factors. Perhaps we can try and compose a top ten, if that's possible.