By non-discounted, I don't mean that you have to have bought it at launch price, just that it, well, wasn't discounted when you bought it

And no, your MGSV copy you got with your new Nvidia 900 series GPU doesn't count (neither does other GPU bundles)

I've bought three. Sanctum 2, Rocket League and Broforce. Sanctum 2 and Rocket League were well worth it, Broforce was alright, at least I got some co-op fun out of it.

IIRC

Portal, Dark Souls, Metro Redux, Five Nights at Freddy's, Mega Man Legacy Collection, and MGSV.

I can only think of one. Portal 2. I did buy GTA V for a friend. But thanks to an error on steams side. And him being in Australia. And R* saw Americans buying GTA V cheaper , to give to aus. I got a refund. But the game never got taken out of my gift box. So... I sent to to another friend, after launch, lol. Everything else was bought when they're old, bundle, or friend gift. Then the rest were bought as physical copies. I don't count those.

Let's see, Mega Man Legacy which I got just recently. Team Fortress 2, all the way back in 2009 when it was still launch price ( I think), Age of Empires II HD which I pre-ordered a few years back, Ikaruga last year and I think that's about it.

5 out of about 100. Secret of Monkey Island Special Edition 1 and 2, Tales from Monkey Island, Tomb Raider Reboot and Star Wars Knights of the Old Republic 2

I think only two.

One would be Bioshock Infinite but even that came with Bioshock 2 and XCOM: Enemy Unknown for free so that's kind of a discount.
The other one is Ori and The Blind Forest

0 out of ~1300 games...

my entire steam library consists of

Portal: steam gave this to me for free

I think I bought only Bit.Trip Runner 2 and Castle of Illusion for full price, everything else was bought on sales.

none. and very little on sales. most games come from bundles or grey market key sellers