Logitech's MX500/MX518 is the best mouse ever. Ever. Logitech knows this too! Which is why the G400 is simply the MX518, rebuilt with a more modern 3600dpi optical tracking engine, 1ms polling rate and smoother polytetrafluoroethylene feet.
Rated for 10 million clicks, it should last until Logitech brings it back for another spin. And it'll probably still be the best mouse ever. It's $50. [Logitech]