The bounce bug occurs for 8ms movement when you fall from certain heights. Three such heights are 296, 512, and 1248 units high. You can find such bugs by testing every height you fall from to see if you bounce (duh). You can also load up a map in a Q3 map editor and look for ledges that are the heights of the numbers I just mentioned. The ztn bounce is 512 units high, btw. I've found that each standard ID map has at least one place to bounce.