6. 'Out of My Mind'
Pearl Jam had just wrapped up "Elderly Woman Behind the Counter in a Small Town" during the encore of an Atlanta show in 1994 when they decided to simply make up a song on the spot. The result was the jammed-out "Out of My Mind," a bootleg favorite they released as the B side to "Not for You" the following year. After a 15-year break, they revived it at their legendary 2009 Halloween show at the Spectrum in Philadelphia.