Gallimaufry
Map: http://www.bungie.net/Online/Halo3UserContentDetails.aspx?h3fileid=94586046
Game: Bungie.net : Halo 3 File Details

Gallimaufry is a single player puzzle map. I've been playing and making quite a few puzzle maps lately, and I've been getting inspired a lot. I've had rushes of ideas for puzzle maps, and I wrote them all down. This map is the combination of those ideas. Most, if not all of these ideas are ones you've never seen before in Halo 3.
An example is the first level in Gallimaufry. It's a puzzle that has you entering a teleporter with momentum to pop out of another one and get somewhere. It has you focus on finding ways to get height, to get momentum.
It is possible that this idea was used before, but I've never seen it. Expect to see many original ideas in the map.
Please note that this map was not meant to look pretty. I forged it generally neat and did some interlocking, but it definitely doesn't look perfect. This map's purpose is for me to share my ideas with the world, not for me to spend hours restarting the round to get the interlock JUUST right.
What I think is a really great feature of this puzzle map it that it doesn't require an extensive knowledge of Forge to beat. You use logic and wit rather than Forge mastery. You don't have to know things like how items would respawn above anything in their way. However, there are some things you should know, like Radar Jammer Jumping, and Grenade Jumping.
Also, there are definitely NO WALL CLIPS. I hate 'em. Not only are there no wall clips, but nothing is ever hidden from you. You'll always know where everything is, so don't think you'll have to find a secret hole, or a tiny item in the ceiling.
Anyway, picture time!

A view of my amazing hub, note the way you can use the radio antennas to make checkpoints.

Level 1, inspired by Portal. A momentum puzzle lies herein.

Note: There is one Gravity Lift in Level 1 that doesn't respawn. As much as I hate to do that, it was necessary to prevent cheating. This is the ONLY part in the map that this happens, and it's at the very beginning, so it's no big deal.
Another note: There is a part in this area where a Gravity Lift is supposed to slide down to you. If it does not slide all the down, DON'T THINK YOU NEED TO RESTART! There are ways to make it come to you.

What's above that pallet?

Level 2 spawn area. Nothing special here.

The top of level 2. What's with that slide?

The end of level 2, but how in the heck does one get up there?

The level 3 spawn area. There's a hole in the wall up there. Hmm.

The ball. How do I get it down? What is its purpose?

This Radar Jammer involves a very fun jump challenge.

Level 4. Finally outside. What's that arrow pointing to? Could it be... the Oddball! One final challenge is between you and freedom.

A nice view of outside levels one through four.

Weapons: Initially, only the Energy Sword. The BR is found somewhere, as are Plasma Grenades.
Health: Invulnerable.
Speed: Normal.
Length: A speed run would last under five minutes. If it's your first time playing this map, expect it to take at least an hour.
Testers: Me, MangerAN and ActualGlory

FINAL NOTE: Not an excruciating amount of time has been put into testing. While I highly doubt there are any breaks, if you feel that you found one, please report it to me.

EDIT: I just put up a video tutorial onto my File Share. Would've made it a video, but I don't have a capture card. Only use it if you're stuck. Here's the link: http://www.bungie.net/Online/Halo3UserContentDetails.aspx?h3fileid=94157830

Map: http://www.bungie.net/Online/Halo3UserContentDetails.aspx?h3fileid=94586046
Game: Bungie.net : Halo 3 File Details