The interesting one to me is the broad jump. For one, it's a gauge of lower body power which is one of the most useful attributes at any position in football, and two, from what I hear, it is essentially genetic / non trainable. You've got what you've got.
There was a post on a forum I saw where a guy tried to predict what metrics led to successful pass rushers. This dude found that 69% of DEs that got 20 sacks on their rookie contract had at least a 9'9" broad jump and a 7.20 3-cone. It almost makes too much sense, cause burst and bend is exactly what you want to see in a DE. Keep those two numbers in mind when you are looking at Combine results this year.
https://www.reddit.com/r/NFL_Draft/...ck_easy_way_to_tell_if_an_edge_rush_prospect/
Also, 40s are almost so overrated that they're now being underrated. For RBs especially, you can sieve out players pretty well just by knowing their size-speed combo. Football Outsiders uses a metric called Speed Score, which is weight * 200 / (40 time ^4). The 200 is just a scaling constant to make easier to read scores. Anyway, a starting level back should have a Speed Score over 100, and anything below that starts falling into the danger zone.
And also, 40 and broad/vert are some of the more predictive metrics for LBs too. Don't have any trend data for this, this is just something I've noticed spending way too much time on Mock Draftable. But look up any good LB you want right now - Kuechly, Wagner, LVE, Sean Lee, Hightower, Mosley, McKinney, whoever - and I bet you his 40 and jumps are all 70th percentile plus. Tape is big for LBs because diagnosing and reading plays correctly is the #1 attribute that linebackers can have, but if you can find a fast, explosive guy that can also read, he's probably a keeper.
https://www.mockdraftable.com/
This got a little bit longer than I thought it would, but I've been looking at metrics more heavily the last couple draft cycles to complement the eyeball test, and I've spent some time trying to pin down what works.