My finalists would include Blake 9.69, Bolt 9.63, Makhloufi's Olympic 1500m, Eaton's deca WR, Merritt 12.80 WR, Felix 200m at trials, 4x100 WR Jamaica men, 4x100 WR USA women, among others.
Note that I believe all of these types of performances to have been juiced, except for possibly Eaton and Felix.
It's tough to pick just one. I would eliminate Bolt and Blake because there is precedent for them both. There is also precedent for Makhloufi's time and winning style.
Of all the performances, I'd have to say the USA Women 100m WR was the biggest. There have been some great relay teams in the past, but this time crushed everything, blowing away a massively juiced record in the process. It is, IMHO, a testament to the systemic quality of athletics, and is therefore more important than the performance of any single athlete. Likewise it is more important than the Jamaican men's 100m WR because they only broke their own WR, and everyone believed it possible, and many predicted it accurately--I myself was off by only .01, having had Powell instead of Frater on 2nd.
That women's 4x100 is huge, absolutely huge. Imagine somebody taking down the women's 100, 200, 400, or 800, or any of the Chinese records.
IMHO it heralds the dawn of a new era in women's T&F, where in order to compete with the guys (who have been breaking WR's left-and-right) more successfully, a new echelon of incredible times will be achieved. The new 4x100 WR is a harbinger of things to come, just the same as Blake's 19.26 was last year.
Blake's 19.26 last year foreshadowed the fastest-ever Olympic 100m final this year, his own 9.69 and Bolt's 9.63, Merritt's 12.80, etc.
Look for women's athletics, the sprints in particular, to become more exciting than the men's in the next couple of years, as they play catch-up. IMHO their rate of improvement will be significant, and some unbelievable records may very well fall before Rio. Jeter has already equaled anything FloJo ever did in the 100 except for the 10.49 Felix is, incredibly, closing in on the 200. Pearson is widely believed to have a good shot at the 100mH. These are all bogus records once thought to be unbeatable.
The USA womens 4x100 WR begs to differ.