Disclaimer: This question is very similar to another (Did Thanos pick them on purpose or was it random?) but I have some caveats I'd like to discuss and/or clarify. Hopefully this won't be closed as duplicate. At least not immediately. I will address the answer to this other question in my question.
When Thanos snapped his fingers with the fully decked Infinity Gauntlet, many died. However, if we look at certain encounters, there seems to be a correlation between interactions and exclusions from the culling.
I'd like to postulate that Thanos, consciously or not, let certain individuals live. During the movie we see that Thanos is not a mindless murderer without empathy. He shows demonstrable love for Gamora (albeit to her demise), and does not slaughter needlessly after achieving small goals, but rather retreats.
Let's look at some individuals who survived the entire movie.
Captain America went against Thanos in a one-on-one, wrestling with Thanos' left hand in order to prevent him from closing it into a fist. We see Thanos punch Steve aside, but afterwards, we see Steve with only a tiny scratch, handsome as ever.
I postulate that Thanos developed a modicum of respect for a seemingly regular human with what must, from Thanos' perspective, seem like a minuscule improvement in physical strength compared to other humans.
Steve Rogers was not included in the culling.
On Titan, Thanos and Stark engage in a brutal one-on-one, after Thanos has incapacitated the rest of The Avengers present on the planet. In this fight, we see Stark fight with tremendous skill, but ridiculously outmatched in the end For the first time, his suit is left permanently ruined by single combat.
Stark sits down on a rock, realizing he is completely powerless, having spent all his resources; suit, body and all. He visibly resigns himself to the loss.
After all of this, Thanos doesn't deliver a final blow. He explicitly expresses his respect for Stark.
Tony Stark was not included in the culling.
Consciously or not, Thanos is not included in the culling. I will not make an elaborate case for why this is. At the very end, we see him smile, but judging from the fact that he went back to a ruined planet (Titan) to look at the devastated remains of his home, completely alone, it seems like a temporary rest after a few days of hard work. Pure speculation of course, but he seems to have a further plan.
A man with work to do isn't going to submit himself to a 50/50.
Answer to a similar question
A good point made in this excellent answer to the other question I mentioned in the disclaimer, was that he has no reason to kill any particular member of the Avengers. They weren't able to stop him as a group when he had some Infinity Stones. They certainly pose no threat decimated one way or the other, when he has all Infinity Stones.
This is why I bring up the idea that he may have spared individuals subconsciously. Perhaps a lingering feeling of respect prevented him from killing certain individuals?
Is there anything to suggest that Thanos may have spared certain individuals, either consciously or subconsciously?
Or likewise, is there anything to suggest it truly, truly was purely random? (That is, despite the "he has no reason to care" argument.)