AMD K6-2 500AFX
The AMD K6-2 stretched to 500MHz. One of the fastest regular K6-2 models (533 and 550MHz models exist too).
Basically the K6-2 ran fine however it did have a few weak spots: a slow FPU so it wasn't really suitable for gaming and that didn't help in reviews. The K6-2, being cheap, was also built into cheap systems which were often more troublesome (and the K6-2 was, unjustified, to blame). Lastly it couldn't keep up with Intel's Celeron-line.
The good thing is that the K6-2 was cheap, ran fine on cheap and/or existing motherboards. Being on the budget it could be a fairly capable system if you didn't want to play FPU-intensive games.