LEGO Half-Life Rail Cart with Tracks and Switch
This is the rail cart from the first Half-Life game, from the episode "On A Rail". This build is fully functional, you can push it along the track and rotate it on the turntable to switch tracks.
Some Xen stuff must be going on with all that green light.
I originally built this when I was a kid. Half-Life was such a big influence on me that half the stuff I built was based on Black Mesa. Of course, the rail cart wasn't this detailed back then.
Photo gallery
Budget version
This concept works without the tiles too, although that makes it a bit bumpy and noisy. However, it's a nice, cheap alternative. This works because the rails are offset to the side by half a brick, making them impossible to connect with the cart's base plate.
The budget version I used as a kid, featuring the classic 3404bc01 turntable.