The Motherload
I'd say I've got a few:
Simpsons: 1-100 (with several alternate versions)
Bart Simpson: 1-20
Bart Simpsons Treehouse of Horror: 1-10
Itchy & Scrachy: 1-3 & Holiday Hi-Jinx #1 (with several alternate versions)
Radioactive Man: 1, 88, 216, 412, 679, 1000, 1 (80pg, Colossal), 100, 222, 136, 4, 575, 106, 8 (Movie Adaptation), 32 (with alternate covers for #1)
Bartman: 1-6 (with alternate front covers)
Krusty: 1-3
Lisa: 1
Futurama Simpsons Infinitely Secret Crossover Crisis: 1 & 2
Bartman and Radioactive Man: 1
Simpsons Comics and Stories: 1 (Regular size and small size from butterfinger bag)
Simpsons Comics (UK Burger King)
The Official History of Bongo Comics (135/750) **
Bongo Comics Group Spectacular (290/1000) **
Bart Simpsons Joke Book (Still sealed in Hero Magazine)
Compilations:
Bart Simpson's Treehouse of Horror: Spine-tingling Spooktacular, Heebie-Jeebie Hullabaloo & Fun-Filled Frightfest
Big Book of Bart Simpson
Big Bad Book of Bart Simpson
Bartman The Best of the Best
Simpsons Comics Belly Buster
Simpsons Comics Unchained
Simpsons Comics Big Bonanza
Simpsons Comics Royale
Simpsons Comics Extravaganza
Simpsons Comics WingDing
Simpsons Comics On Parade
Simpsons Comics Madness
Simpsons Comics Strikeback
Simpsons Comics Simpsorama
Simpsons Comics Spectacular
Simpsons Comics A Go-Go