I made this video to demonstrate how a Frequency Counter can be used to augment the measurement system on an oscilloscope. In this case, I need an exact count of the number of pulses in a 1 second period. I use the Totalize function on a Tektronix FCA3120 to count the dropped pulses produced from a Tektronix AFG3252 function generator. As you can see, the deep memory Tektronix MSO4104B oscilloscope can measure quite a few pulses with 20M of memory, but nowhere near a continuous 1 second or longer period. In this case, the frequency counter is the ideal tool.
One technical note--although Frequency Counters are available up to 40GHz in bandwidth, various techniques are used for making this measurement that would miss a single dropped pulse. The Totalize function is limited to about 160MHz, or pulses that are about 2ns wide.