A proof of concept I made a while ago, thought I might as well throw it out here too.
Credits: some surf map I forgot the name of where it was used in 1 small area.
A quick and really bad quality video I recorded to get an idea (download below, no regen or teles):
I have never encountered a bug while skipping off of and sliding off the platforms of the size as seen in the video, 1024x1024 units, but when I tried out a bigger platform where I could strafe around in circles eventually I would get stopped after a while.
Something to keep in mind is that teleports are server side but this won't pose a problem for people with normal ping to servers.
How to make it:Basically a teleport with an offset of 0, the player moves normally while flying through the teleport but the floor has 0 friction and you cant jump from the floor.
In this case the destination is right on top of the trigger_teleport but it can be anywhere and you can re-use the destination for multiple platforms but I am not sure if the distance of the destination to the trigger_teleport makes it buggy, best to just use a new destination for every trigger_teleport and make it float above the trigger_teleport.
You can combine it with water for the usual stronger boost from rockets, used on almost all the platforms in the video.
On the right you can see the water is 1 unit above the platform. I am not sure why I did that since I made it 2 years ago. I think I did it because I first placed the water touching the platform at first but then it didnt render the topside of the platform.
Yes it is called farts9, if you want to compile the map as it is right now you need to disable vvis and vrad:Download (.vmf):
http://www.mediafire.com/file/2cis9z887d74jl7/farts9.vmfDownload (.bsp):
http://www.mediafire.com/file/o2cwpdic208bd1u/farts9.bsp