Throwing this here in case someone is interested in a category that doesn't yet exist. I'd rather not create a new category until there's actually a (planned) run for it, never liked the look of leaderboards with tons of empty areas. (As of this writing it's still pretty blank, but I'm aiming to fill it.)

I have some current thoughts for categories (both full-game and missions) that I may or may not get around to:

• Any% (Missions): Complete an entire mission, as fast as possible. I could've started with this, but All Challenges is a better demonstration of the game.
• Currently there are no missions set for "Toxic River" and "Infernal Gate", as there isn't a meaningful All Challenges for them, but naturally those can be added.
• Changes to what items are allowed. The most obvious is "No Items", where the player has nothing equipped. I can also see items split between those found in missions ("Search-only/less"), purchased in the Item Shop ("Silver-only/less"), or purchased at the Curator Animarium ("Soul-only/less").
• All Challenges (Full-game): Start a new-save file and complete the game, while also successfully completing an All Challenges run on each applicable mission.
• 100% (Full-game): Start a new save-file and keep going until it's a 100% file. Timing could have the player return to the main menu to confirm this, but (currently) having the Item Shop and Curator Animarium closed for business confirms this.
• Might wanna look into Low% (Full-Game) but I think this would force the player to deliberately lose challenges, which includes the time challenge, and therefore have a lot of wasted time in it.

If any of the above generate interest, or you have something else in mind, this is the place to ask!

DOSBOX: Don't change certain settings to gain an unfair advantage, cycles, for example.

This is entirely fair, but what is the "unchanged" setting for cycles? The GOG version comes with a .conf of "cycles=fixed 8000", and I suspect that's a common use case: anyone owning an original copy, however, would likely install DOSBox manually and therefore have a default .conf of "cycles=auto" (which should result in a fixed 3000). So there's already a disconnect between naive runners.

The cycle setting (others can matter though very few ever do for timing/playability) is always going to be arbitrary, whether technical or aesthetic. Most games don't throttle their speed appropriately, M&M3 included, so it often comes down to what runners find necessary and/or sufficient. My own run from a few years back set cycles to fixed 20000: according to the description, "The cycles are to keep the game at a steady but brisk pace, allowing area transitions to occur quickly." (To be clear, I'm not here to argue whether my choice is better, and have no intentions of forcing a different-cycled run into the leaderboard.) By contrast, my Swords of Xeen run set max cycles because of the continuous saving/loading, which crashes way more often without it (though at least in this case, the GOG .conf also coincides here).

Regardless of what is chosen, I recommend clearly stating settings necessary for a consistent leaderboard. The GOG standard is reasonable here, but I've used DOSBox with many games and can tell you GOG doesn't always come up with settings I consider good for even a casual experience. Their settings are no less arbitrary than others that could make the speedrun more enjoyable to play.