Here's one I prepared earlier! (It's from the ill-fated tournament I ran last year...)
Play Sonic 3 and Knuckles with any character. You may start from any act. You must collect the following items: 10 rings, Speed Shoes, invincibility, each of the 3 types of shield, 1-up, Robotnik, and a large ring. Your run ends when you collect the last item, and your time is the sum total of all levels played.
Now, if you competed, please do me a favour and -don't- spoil the optimal solution...