Alrighty, feel free to add your own list or comment, I used to do this all the time in middle school.
20: King Crimson
19: The Lord Weird Slough Feg
18: Rage Against the Machine (The band that got me into rock and my first concert)
17: GG Allin and The Jabbers (Back when GG was a decent singer)
16: The Misfits (Danzig and Micheal Graves eras, I HATE Jerry Only)
15: Husker Du (80's Hardcore, I reccomend Zen Arcade)
14: Black Flag (Not so much the Rollins Era)
13: Janes Addiction ( I Wish they could put out a new albm)
12: Body Count (Ice-T's Hardcore band)
11: Bad Religion (From 80-85 to Suffer)
10: GWAR (Greatest Live show of all time)
9: The Electric Six (Danger Danger! High Voltage!)
8: Bad Brains (Essential punk band)
7: Thin Lizzy
6: Blood For Blood (Boston Hardcore)
5: Anthrax (Persistence of Time is Essential for any metal collection)
4: Tad (Seattle Grunge Band)
3: Megadeth (Mustaine is a Dick, but his band dominates)
2: Blind Guardian (EPIC METAL!)
1: Iggy Pop and the Stooges (Got to see them live last year, Greatest Night of my Life)