There are many types of flash drives available to suit all different kinds of use, but to keep things simple we'll break things down into five different categories - Generic, High Performance, Ultra Durable, Secure, and Novelty. Of course, these categories are not all mutually exclusive. For example, a Secure flash drive with hardware encryption may also be Durable enough to withstand the crushing forces of a Honda Accord.
What we like to think of as Generic flash drives are the most common type sold, build for economy and raw capacity but not necessarily speed, and almost always encased in plastic. With the exception of a few manufacturers like Kingston, just about any flash drive with a product name that doesn't have a Mountain Dew-inspired suffix like "Extreme", "Lightning", "GT", "GTR", "Turbo", or "Ultra" will typically fall into this category. Likewise, any product that has such a suffix or is labeled as a high-end model would fall into our High Performance category and will employ higher-binned flash memory chips and better memory controllers to increase transfer speeds.
Ultra Durable flash drives can be either fast or slow, but are by far the most fun to review because we get to beat the crap out of them, all in the name of journalism! These can be encased either in rubber or a metal alloy to protect against impacts, and they may or may not have a watertight seal for the USB cap. Depending on the design, manufacturer's claims, and your definition of common sense, these babies can withstand drops/throws from the top of a building to a concrete surface below, are more likely to survive several rounds in the washer and dryer (if allowed ample time to dry before use), laugh at the notion of being baked in an oven, and love to be submerged at the bottom of a diving pool. Better still, some can deflect bullets up to a .50 caliber, or withstand the almighty crushing forces of Honda automobiles.