A list.

Today I went to the Epicenter 2010 show and I had the best time EVER seeing Blink 182 and Bad Religion (also, Rise Against, 30 Seconds to Mars, but whatever.)
Anyway, I realized how many shows I've been to and I thought it might be a good idea to start making a list right now, even though there are definitely bands/artists I will forget.
So, (in no particular order except how they come to mind):

Blink 182
Bad Religion
Rise Against
30 Seconds to Mars
The Matches (more than any other band, around 7x!)
Laura Veirs (2x)
Minus the Bear (2x)
Snoop Dogg
A Tribe Called Quest
Wu Tang Clan (plus Method and Red a separate time)
Rakim
KRS one
Murs and 9th Wonder
Immortal Technique (2x... ugh)
Brother Ali
Jedi Mind Tricks
Hieroglyphics (del!)
Bad Brains
Slipknot
Cypress Hill
Sublime (sans Bradley)
Geto Boys
Pennywise
Pixies
Buzzcocks
Dead Man's Bones
Man Man
!!! Chk Chk Chk
The White Stripes
Jimmy Eat World
Motion City Soundtrack
Green Day
Paul Simon
Brian Wilson
Hall and Oates (2x)
The Turtles
The Lovin' Spoonful
Of Montreal
MGMT
Sam Roberts
Ben Kweller
Sufjan Stevens (about to be 2x!)
The Decemberists
The Shins (2x)
Viva Voce
Belle and Sebastian
Imogen Heap
Rogue Wave (2x)
Death Cab for Cutie (2x)
Plain White T's
Roses Are Red
This Day and Age
A Thorn for Every Heart
Aquabats
Backstreet Boys
NSync
Britney Spears
Mandy Moore
Gwar
Steve Aoki (also, Rivers Cuomo and Lil John)
Infected Mushroom
Deadmau5
Cascada
Built to Spill
Eagles of Death Metal
Young Galaxy
Madonna
Reel Big Fish
Streetlight Manifesto
Suicide Machines
The Hives
Ok Go
From First to Last
I Am Ghost
Dashboard Confessional
Brand New
Sage Francis
Yo La Tengo
Styx

These aren't even necessarily bands I even like, some I just remember because I bought a shirt or a poster which helped me remember...
LET ME KNOW IF YOU CAN THINK OF ANY I'M MISSING.