Boy this one's tough. Couple runner-ups are Santa Monica by Everclear and On My Way by Rusted Root. But I think the winner is:
If I Should Fall From Grace With God - The Pogues.
Definitely my favorite song at the moment. Though, if I had to die at the songs end as you indicated i'd be pretty inclined to make 'As Slow As Possible' (639 year track length) my new all time favorite song
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