Recording high speed video can be prohibitively expensive — especially at a decent resolution. It's not uncommon for the price of a quality high-speed video camera to reach into six figure territory. YouTuber Smarter Every Day, however, hacked his normal SLR to make a slow-motion shot of bullets flying through the air and smashing through matches.
So, how did he do it? With a very precisely timed flash and camera synchronization. They clamped a gun in place, and fired tens of shots at a specific target. For each shot, the flash and camera fired a little bit later in the process. These images were then stitched together to create a slow motion effect, as the bullet moves through the air. Yup, it's just like stop-motion animation, but using objects actually moving rather than carefully placed and positioned.
The shooting rig was a Canon T1i, lit with a 580 EXII strobe, set to 1/128th power setting, and the shots were taken at 50 microseconds incriments.
Unfortunately, it's not something you can easily do at home, as they used a very, very high end piece of technology to make sure the timing was perfect — a Quantum Composer Pulse Generator 9520. It's still a very cool example, though.