First and foremost, as someone else mentioned, the experience of playing with them....I'm "mattfromcanada" from Dublin, June 25 2005, got to play 'Party Girl'
Had the guitar picks, but they were in my van when it was stolen (nooooooo!!!!)
Other than that....
Every 7" release from Three-Vertigo with the exception of 'Another Day' with P/S....have just the vinyl though
My Hometown Croke 85 Bootleg on Vinyl
Backstage Passes from PopMart (cousin was tour accountant with TNA)
'Thanks For Shopping PopMart' signs from the K-Mart tour kick-off (see note above)
this is very cool.....Bottle of wine leftover from the PopMart kick-off party in Las Vegas....probably pretty bad now...maybe I'll open it for my first-born

Three 7" signed by Bono in Toronto, 2001....sunglasses over Peter's eyes
Larry's drumsticks leftover from PopMart Chicago soundcheck
All albums except ATYCLB on Vinyl
Best of 1980-1990 Radio promo disc w/ selected tracks (incl Trash, Trampoline And The Party Girl)
Many many photos and video clips of my Dublin experience
And perhaps the best thing I got from U2....a gateway into the music world. I didn't listen to music before U2....they've broadened my horizons....
No, playing with them was way cooler, but that's still a good bonus!