The favourite short benchmark
Five seconds is long enough that luck hardly matters (one click is 0.2 CPS) and short enough to stay near full speed. Start at about 90% rather than flat out, hold the pace through the middle and finish hard.
Good 5 second scores
Most people get 33 to 40 clicks (6.5 to 8 CPS), usually just above their 10 second score. Around 45 clicks is fast, and 60 or more usually means jitter or butterfly clicking.