I've filled in all the results we have so far. Some trivia regarding this challenge:
* Of the levels possible with 1 skill type, Gentle 10 "Downwardly Mobile Lemmings" has the greatest variety of solutions, with six 1-type solutions (everything except climbers and floaters).
* Six is also the greatest variety of equally good solutions among levels needing more than 1 type, with Quirky 31 "Cascade" having six 3-type solutions.
* And since six is the magic number for this challenge, it's also the highest number of skill types required by any one level, with three levels needing 6 types: Gentle 28 "Catch more floaters", Quirky 29 "Tension Sheet, Good Idea" and Manic 10 "ROCKY VI". (Of these, Gentle 28 is the only level in Gentle requiring more than 2!)
* Levels solvable with 2 types nearly all require builders and a destructive skill. Roughly half have builders+bashers as either the only 2-type solution or one possible solution.
* Builders+bashers+diggers seems to be the most commonly occuring 3-skill combination.
Looking beyond Redux, I know of at least two levels, in packs restricted to the classic 8 skills, that require 7 skill types: "Academy of Eight" in DoveLems and "Playground" in Lemmings Migration. Both of these are 1-of-each levels. I don't know of any levels that require all eight skill types, but there are a lot of packs out there, and 1-of-each levels are popular, so I wouldn't be surprised if we find one!
EDIT: How could I have forgotten? My own level "Rhapsody in Blue" is a 2-of-each and requires all eight types. It's a Cheapo level that has also been remade in Lemmix and Lix, and is part of Revenge of the Lemmings, so it should be coming to NeoLemmix at some point....
In packs not restricted to the classic 8 skills, "POOR WEE CREATURETTES" in Lemminas requires 10 skill types.
