I don't remember ONML that well as I haven't played it nearly as much, so I'm doing two seperate lists for the two games I *do* know well: Original and Lemmings 3D.
EDIT: I've modified this to include a couple of levels I forgot about before.Original5 Worst5 - Hunt The Nessy. Long building stages are alright for earlier in the game. One in the middle of Taxing, especially one of this length, is just pointless.
4 - The Prison. This level is plain and simply annoying.
3 - Save Me. It's a pain to pull off, and long yet overly simple to work out. Hard to pull off levels, in my opinion, should either be short entirely, or at least have the hard to do parts near the beginning.
2 - All or Nothing. It's either plain luck, pixel-precise mouse location, or if you have a version with the arrow keys feature, a total dud level.
1 - We All Fall Down (Taxing). This level is plain annoying. The fun one is a good early-game introduction to the idea, the Tricky one is still reasonable, and the Mayhem one requires a bit of additional thought beyond the normal for these levels. The Taxing one is just boring and tedious.
5 Best5 - Postcard from Lemmingland. This was the first level in Lemmings that had me stumped for a while. It's a great puzzle, without any difficulty in how to actually execute it. (Some levels have overtaken these two.)
4 - Take A Running Jump. While not exactly challenging, it's a very interesting design.5 - Upside Down World. This is a really fun puzzle level, that takes a bit of thought without being overly difficult.
4 - Mind The Step. I really have no idea why, but this is simply a level that I love playing.
3 - Menacing. No, not the PC/Amiga level. The Sega Master System one! It's a very creative level that uses a trick that I don't think the original game ever uses elsewhere (ok, Feel The Heat does, but that's it) - took me ages to work out how to do it, I kept thinking that couldn't possibly be enough builders! My only complaint is that this level would probably have been better off in Taxing (or possibly even early Mayhem) rather than Tricky.
2 - No Added Colours or Lemmings. A great puzzle level, which is the kind I like. Almost as good as...
1 - It's Hero Time. This level focuses on solving a puzzle in a creative way, and obviously gives a lot of variety. On top of that, with how many different solutions there are, it's fun to play over and over. A truly excellent level.
Lemmings 3D5 Worst5 - Stilt Walkers. I don't know why, but this level is just annoying to me. Not to mention the huge backroute.
4 - Spaghetti Junction. Mazes and splitters are very overused by this point of the game. Of course, there's the backroute, if you can find it.
3 - Tower of Lemlab. This level is basically just about passing typical obstacles one by one, with no overall theme or challenge to it... unless you find the backroute.
2 - Jelly Belly Islands. Basically, it's about remembering where the teleporters send you (Yet again, unless you find the backroute
). It's plain annoying.
1 - Final Maze. Yet another remember-where-teleporters-send-you level (or in this case, springs). And do I even need to say it? Backroutes FTW.
5 Best5 - Dot to Dot. Okay, yes, it's a build-build-build level. But the fact that there isn't many of them in L3D makes it more acceptable. Besides, I dunno why, but I always found this level quite fun. (And of course, gotta love the shortcut!)
4 - Across The Network. A fun level with several solutions, all of which require a bit of thought to pull off.
3 - Lemmtris. It's fun to have a more olden-style level among the game. It's also notable for being the only non-training level where 100% can be acheived, yet is not required.
2 - Rescue Team. Okay, the level itself wasn't done that well, but the idea behind it is still a great one. It's pretty fun, too.
1 - Critical Path. Possibly the only level in Lemmings 3D that qualifies as a true puzzle. It's great fun.