Sigma SD1 Merrill
The SD1 is a no-frills SLR with a very basic feature set that offers exceptional image quality at low ISOs (100-400). However it's let down by slow file write times and erratic control behaviour during this process. High ISO image quality is unremarkable, and there's no live view for tripod shooting. It's a specialist tool, but if you can live with its limitations, it's capable of excellent results.
Photographers looking for exceptional low ISO image quality, and willing to spend the time processing RAW to achieve it.
Sports, action, or any kind or photography requiring high ISOs