The single most popular hobby use case may be the Mister project for near perfect, super low latency retro gaming emulation. Another common use case is real ti

The single most popular hobby use case may be the Mister project for near perfect, super low latency retro gaming emulation. Another common use case is real time video stream manipulation. There is a demo by Bunnie Huang who uses an fpga to intercept, decode, then reencode HDMI video streams (including microsecond timing manipulation of one of the data lines) in order to do video overlays on the video (for things like captions). In general the main use cases are really for things that require lots of parallel and/or low latency processing.