Ok, so up front, I didn't actually go hands-on with any games on the show floor at PAX South. I was very much content wandering the hall and watching as others played rather than wait in the lines to play anything myself. That said, these are the games that looked really intriguing and cool to me so I'll be keeping an eye out on them and would encourage you to do the same.
HAUNTED: Halloween '85 - A side-scroller beat 'em up on Steam Greenlight and available on an NES cartridge. This one caught my eye because it indeed was being played on an old school Ninendo. So I sat there watching as the player ran and jumped through forests and a high school punching zombies and ghosts.
Rivals of Aether - Rivals of Aether is a Super Smash Bros.-esque brawler with elemental animal warriors instead of iconic video game characters. It's available on PC and Xbox One.
Bugs 'n Boo Hags - The thing that intrigued me about Bugs 'n Boo Hags was its tagline: "Inspired by the History and Folklore of the South Carolina Lowcountry." The game is an old-school single screen arcade-y platformer being developed for PC, Mac, and Linux.
Omnibus - I stumbled upon my friends playing this game at the Devolver Digital booth. In the Omnibus multiplayer I saw, they were each controlling runaway buses in a small arena and could ram each other or race around the arena. The goal was to be the last bus upright or still in the arena. It had the look of an N64- or PlayStation One-era game. The guys were certainly having fun with it. It will be available Spring 2016 on Steam.
Overland - Overland was one of four games on display at the Finji booth. Our friend Andy specifically sought it out because he's a huge fan of their art style. And with good reason. Overland appears to be an isometric turn-based strategy game like Final Fantasy Tactics but with the player trying to survive the trip across a broken post-apocalyptic continent instead of fantastical RPG stories. It's coming soon to PC, Mac, and Linux, with a likely console release sometime after.
Night in the Woods - Night in the Woods was another Finji game with a beautiful aesthetic. An adventure game Kickstarted in 24 hours in late 2013, Night in the Dark is coming to PC, Mac, Linux, and PS4 in 2016.
Feist - Feist struck me as a visual mix between Limbo and Ori and the Blind Forest. The third Finji game, Feist is available now on PC, Mac, and Linux.
Panoramical - I honestly don't really know how to describe Panoramical from just looking at it off-screen but as I understand it, it's an interactive experience with an emphasis on creating soundscapes, with the visuals of the world reacting to the changes you make. Bottom line: it looks really cool and sounded really pretty. Available now on PC and Mac.
Knee Deep - Described as a "swamp noir adventure in three acts," the color scheme of Knee Deep caught my eye. An episodic adventure game a la Telltale or Life is Strange, Act III releases in March, with Acts I and II already available on PC, Mac, and Linux.