I don't think I have had any true impulse buys this gen. I have bought a few games I was not planning on buying at the time, but that was because there was a sale. I would have gotten them eventually.
I did have a pretty good impulse buy last gen though. I was in some discount store, maybe a Big Lots or something similar. Then on a shelf with just a handful of crappy games is Baldur's Gate: Dark Alliance for about $20. It was weird because the store didn't really have many games. I recognized the Baldur's Gate name, and snatched it up. It is a pretty great game, and I ended up spending a ton of hours with it.
Switch Code: SW-7377-9189-3397 -- Nintendo Network ID: theRepublic -- Steam ID: theRepublic
Switch - Super Mario Maker 2 (2019)
Switch - Bastion (2011/2018)
Switch - Mario Kart 8 Deluxe (2014/2017)
3DS - Pushmo (2011)
Wii U - Darksiders: Warmastered Edition (2010/2017)
Mobile - The Simpson's Tapped Out and Yugioh Duel Links