This might need to be an Ask PG. I wonder if there is a startup that he recalls passing on that influenced the way (minorly or majorly) he evaluates startups.
Recalling PG's previous answers to this question: there are several instances of successes that YC didn't accept, but it's not PG's place to disclose who did and didn't apply.
It's too early to say (remember it typically takes 7-8 years to reach a major exit event). But SendGrid and LightSail Energy are probably the two that have raised the most money and are public about being rejected from YC.
This is pure HN porn. Entertaining and satisfies curiosity but no significance whatsoever.<p>Edit: Noting somewhat predictable downvotes so I would ask that someone reply with what the significance of a single data point is other than satisfying curiosity? Note also I didn't say it didn't belong on HN or "hey why is this on the front page" etc.