We have covered plenty of awesome marble machines here in the past. Orb Drop II is also worth a look. It is an awesome marble run with wood, plastic, and metal structure and motorized stairs that puts on a mesmerizing show.
The machine supplies orbs to two separate drops. As the maker explains:
The first drop is the shorter of the two and has a 60 degree drop into a loop de loop (3” loop compared to 2” loop on original Orb Drop). The second drop is longer and contains a sequence of small drops and inclines whiling banking around 13 curves. The orbs from both drops finish at the bottom of the stair-stepper to make their way back up to the top.