Bricks, Crystal, Fire, Pink and Dirt.

Almost all my best levels are designed in Brick style(such as Castle Of Oblivion, from Ultimate Challenge 5), or harder versions of Brick style levels(such as The Blasted Road To Lemming High, from the Fewer Builders Challenge).

Crystal is the most commonly overlooked style. For some reason I don't like big levels using it, but it's great for small levels - see "Without What Is Needed"(Ultimate Challenge 1 or Lemmings Plus 2) for a great example.

Fire is an interesting style. It has almost every terrain piece shape you'd need. One of the more overlooked but quite good Ultimate Challenge levels, "The Three Lemmings", uses Fire style for flat platforms, while another one, "Dungeon Of Oblivion", adapts the Oblivion trick into it. The possibility for this style is almost endless.

Pink, I can't really say exactly why it's cool. The colour, maybe.

And Dirt. Although I don't really find it suitable for hard levels, it's pretty much the only style that is good for making any shape without it looking like it's made of blocks.

And ate it's

They work fine for me.

I made the training levels as place-fillers. I couldn't be bothered thinking of anything else.

Check bit further down on the topic list, for the "Fewer Builders Challenge (Downloadable Pack)" topic, for my newest pack. It's in a new topic because... it's unique!

You can now download, as a pack, all the levels that are suitable for Fewer Builders Challenge, with the minimal builders. If I remember correctly(and I probably don't), there are 17 levels. Download it at Lemming Crazy. Good luck, a lot of the levels(especially the last few) are extremely hard - definately worthy of being in Ultimate Challenge 6 or higher... except they're not in any Ultimate Challenge(although two levels were taken from Ultimate Challenge), they're in Fewer Builders Challenge.

Note that three of these cannot be done with the original levels from the packs. These are:

Unpossible! - The original level does not have enough climbers for this solution to be executed.
Complications: Extreme - Some terrain was moved over by four pixels. Without this move, the level is impossible.
Tetra Oblivion - The original level is lacking many of the needed skills for this solution to be executed.

Click here to go to Lemming Crazy.

I've made the pack, although I still have to look through Ultimate Challenge for some extra ones. Anyway, for people attempting them either way, here's some tips:

-Practice your bomber timing. You need it for Funny 4, Strange 11 and Neutral 2.
-Try stretching your builders out, although there's only one level as far as I remember that this is any important.
-Practice pixel precision. This is required at least twice.

Someone made "Oblivion Xtreme", which...