The first and most commonly known are the Summer Specials these were purely Sonic Comics unlike normal comics and contained an assortment of different extra content such as competitions, and games to play. As far as I know these where produced in 1994, 1995, 1996, and 1999 (The Summer Special of '99 was also only reprints).

          Another special edition comic that is commonly known about but quite rare to actually own is the Knuckles Knock Out Special which was released in the summer of '96 it was very much like the Summer Specials but was completely Knuckles orientated. There was only one issue of this made.

          There was only one other non-sonic full special edition issue and that came in the form of the Eternal Champions Special Edition. It was produce around the time of the Mega CD apparently to boost sales and contained comics strips, character stats, competitions among other things.

          The last set of special edition comics are the Poster Mags these where normal sized issues that folded out to reveal an A1 poster, the content of these varied widely; anything from game walkthroughs to 6 page comic strip additions to the regular editions (Streets of Rage and Shinobi). The poster Mags where produced from late 1993 - late 95.