Track pad: call of duty infinite warfare, runs and looks surprisingly good on Deck and trackpads were a lot of fun to use with it. I don't play multi, just single player. ace combat flight game i used the track pad too and enjoyed it. also just being able to navigate in desktop mode with the track pad is kind of handy from time to time.
It's hard question to answer, but I will try
Final Fantasy X HD Remaster (Runs at 4 watts, takes 5 seconds to set in steamOS, gives about 10 hrs battery life in airplane mode, eat your heart out windows handhelds, key being how quick it is to dial it in for every game on SteamOS vs windows) (i did use trackpad sometimes in this game, but even better was assigning the back panel buttons to the HD Remaster specific controls, like speeding up time etc, was really nice being able to do that with the back panel buttons instantly, skipping random fights whenever i wanted, but also enabling them when i wanted, etc was just nice and enhanced the experience, being able to do it on the fly is the key though to the smooth immersion), I have always wanted to replay this game since launch day when I beat it in the first couple months of its original launch date in 2002 or w.e, but every time I tried I just couldn't get into it. For some strange reason the Deck LCD and Deck OLED were able to both equally get me back into this game, I don't know why, combination of being able to be more comfortable when playing, form factor, comfort of hands, etc. Also, I had issues with frame pacing on windows sometimes, but no such issues with steamOS running it.
Prototype was another fun game on Deck, damn near impossible to get it to run on Windows, but on SteamOS it runs flawless - this is surprisingly one of the best benefits of SteamOS no one talks about, how many games that are a pain in the ass to get running on modern Windows work so easy on SteamOS, a SteamOS handheld and Windows PC really compliment each other in this regard, as I still prefer PC for AAA games, and lets face it there are a lot of games that just better with mouse and keyboard, diablo IV comes to mine that I recently played I prefer on PC over Deck.
Stardew Valley is another Deck only game for me, because that kind of game is just nice and easy to relax to
Cocoon was another fun game on Deck.