Alright here is a big one. I have been working with two other people on this project for almost a month now. This is possibly the largest rollercoaster that Minecraft has seen. It is 5:23 seconds long and goes from bedrock to skylimit (265 blocks) on Once Upon a Craft. It is fully functional and the minecarts recycle through it so you never have to bring you own. There is a grand finale of fireworks that is amazing to watch. The coaster has been named The Shredder and unofficially called Dropper as it has several large dropoffs, the biggest one lasting more than 16 seconds. 
The coaster was built around a parkour course and then expanded to go thru parts of the course and add a unique touch to the parkour experience. The parkour course is hard, but it can be done. There are rewards set up at the end of each of the four sections of the arkour course. 
Because of the size of this build, we have a small town around and thru the coaster. There are several small buildings which couldf be used as houses or shops. There is a small biodome style building in the middle of a lake that overlooks the start of the coaster. One building is a sattelite dish, and some are houses that were built on our server. Along with the town and parkour course, there is a working elevator that goes to a observation style deck. One of a twin tower style building will be included with this as well since it is near the coaster.
If someone would like a version of the coaster without all the extras, let me know and I will remove as much of the outbuildings as possible and just have the parkour/rollercoaster. 
Come check it out on Once Upon a Craft, at 108.174.60.85:25665, before you download.
Enjoy
Disclaimer: I did not make all of the background buildings and do not take credit for them. 
Builders: FlugzNutz, RenegadeFireman, and myself.
Idea: FlugzNutz