Sony's first portable system. The PSP has been released in four major iterations, differentiated by size and screen, and then by a new form entirely (PSPGo). Hacking all of them is relatively simple, and gives much better load times for most games, access to most of the PlayStation library, and good emulation options. Home to the UMD format, which has set landfills and bargain bins on fire. There is something mildly romantic to the idea of buying Die Hard on UMD and then watching it immediately on a long train ride though.
The PSP has had sort of a tough ride, in that a lot of the games are just iterations of console games but with that PSP look on your PSP.
Now that the PSP is effectively dead and buried in North America and Europe, physical copies of PSP games are becoming increasingly difficult to find at retail outlets, with even trade-in stores like Gamestop phasing out their UMD collection to free up shelf space. Thankfully for the PSP late adopter, most of the system's noteworthy retail games have been made available for digital purchase via PlayStation Network, though a few older titles (circa 2008 or earlier) can only be found on UMD.