Bands, solo artists, record labels, whatever. I have (all t-shirts):
Led Zepellin one from when I was like 12. I ripped the sleeves off and often now sleep in it.
Maxïmo Park, signed by the band
Shout Out Louds
Be Your Own Pet
2Pac R.I.P. (present for my 17th, picked up by a mate in a Thailand market. holds up well)
Pixies from recent Doolittle tour
Errrorplains, given out free
DFA79 I bought off eBay
Franz Ferdinand one I lost in Malawi like 4 years ago :'(
also that Radiohead jacket with the rows of coloured sketched housing they were selling at Reading. and a Busted tee towel I swapped for a Shaun Of The Dead poster when drunk.