What HASN'T been done yet?

1) Well, there's my idea a bit back about where 'Tails doesn't get tired': http://forums.sonicretro.org/index.php?showtopic=8825

2) Another idea of mine would be having minor boss battles in the Special Zone itself!

3) What about having Knuckles do an Alex the Kidd-style punching attack - we've got the sprites for it already [when he's waiting to move], so why not put them into good use? [oh, it's already been suggested at the other said forum thread]

4) How about [if it's possible] have the Super Mario World power-ups [feather, fireball, etc.] in Sonic? Heck, why not just add the all bad guys into Sonic, too [Goomba's, Koopa's, Thwomp, etc]! :P *is shot and maimed to death*

5) Would it be possible to have a type of 'fire beam' coming from Super Sonic's eyes, which destroys whatever's in it's path? that'd be sweet! :D

6) Get Knuckles to swim? -instead of gliding underwater

7) Have a 3-player mode to it [Sonic Heroes 2D!] - or 2 AI characters at once