Just for the fun of it, here's some melt-your-eyeballs chain reaction machines! Amazing creativity!
The Cake Server - Watch this insane machine do its job while the guy peacefully eats his dinner!
Dr. Boom's Epic BOOMSDAY Machine Powered by Fire and Ice - Fireballs, ice slides, rockets, Tesla coils, lightning, and that's just the beginning!
250,000 Dominoes: The Incredible Science Machine - This will totally wipe you out! It's 15 minutes, but the incredibly well-planned complexity of this gigantic domino reaction is worth the watch!
This Too Shall Pass - OK Go is a rock band that created a wacky chain reaction as a music video. Pro Tip: If you don't like the music, or find it distracts from watching the chain reaction action, just mute the sound! If you like this kind of wackiness, here's a couple more links to their insane videos: Upside Down & Inside Out (in a plane, at zero gravity); Needing/Getting (the zaniest road trip ever).
The Way Things Go - This is one of the earliest chain reaction creations to send random items careening into each other to accomplish a task! The link opens a compressed 3-minute version of the chain reaction, which took longer to unfold in reality.
A Better Mousetrap - The creative history of chain reaction machines, of course, must include Rube Goldberg, whose amazing chain reaction machines dominated the comics pages of newspapers back in the day. Indeed, his name has now entered the Oxford Dictionary: Rube Goldberg: adj. (of machines and devices) having a very complicated design, especially when used to perform a very simple task. Check out his wonderful inventions!
Guinness World Record for Largest Rube Goldberg Machine - The 5-minute video greatly compresses everything that happens in this mammoth chain reaction, so you miss details, but the complexity is marvelous as it "gets the job done."