@gamingonlinux For me, definitely the Steam Deck.
Not only because it‘s a great device in itself, but because it led to big publishers like Sony, ActiBlizz and EA actually optimizing their games for a Linux based device.
The whole handheld PC gaming niche is a great way for Linux to get a foothold in the consumer market, partly because Windows is such a pain to use on a handheld device.
Linux gaming was already in a good spot before the Deck arrived, but now I think it has really taken off.