Loved firefighters as a kid, ultimately seeing this character reignited a spark of it. Currently have his V1 figure from 1985 and his 25th Anniversary figure from 2008.
Fan of the original figure's design, and his back-story. Currently have his V1 figure from 1988 and the Rise Of Cobra Wal-Mart Exclusive 'Night Force' repaint of his 2008 25th Anniversary figure.
3. Lt. Falcon
Liked his story (for some reason) in 1987's G.I. Joe: The Movie, and learned to like some of his other portrayals. Currently have his V1 figure from 1987, and his 2008 25th Anniversary figure.
Like the design of his figure. Currently have his V1 figure from 1986 and his V2 figure from 1991.
Heard very good things about his characterization in the comics, and once read, were proven to be true. Currently have his 25th Anniversary figure from 2007 and his V2 figure (the Tundra Ranger version) from 1989.
6. Cover Girl
Her backstory was one of the most interesting I've ever read for a military-themed action figure line. Currently have her figure based on her portrayal in the Rise of Cobra movie.
Love his backstory and the design of his figure. Currently have his V3 figure from 2004.
Who doesn't love this guy?
9. Storm Shadow
Same as above.
Like his backstory, his attitude, and his and Lady Jaye's status as one of the most successful fictional couples.
11. Ice Cream Soldier
The first original-style G.I. Joe figure I ever got. Currently have that figure, and made a flamethrower with pack for him out of spare parts.
12. Lady Jaye
Great specialty, great characterization, and the same as in the comments about Flint.