Just to add to the genre list growing in the comments below this is/would be useful for Devil May Cry players as you can use this to see how close the pros get to frame perfect wave-dashing and also see exactly what frame they jump cancel.

Agreed

Split second moments happen all the time on twitch, frame by frame control for VOD's and clips will go a long way.

Speedrunners like myself want to be able to time the length of speedrun videos to the frame for extra precision. This would be beneficial for not only the runners themselves, but also for the people who moderate speedruns like I do. YouTube already allows this precision and also allows third-party tools to interact with YouTube videos and show a visual display of the fraction of time.

Likewise I play a fighting game competitively and frame data is very important. For example, knowing how much frame advantage I or my opponent has on each others shield is critical. I would properly review my competitive sets, please.