If I had to recommend a single Prime Day deal, it'd be this controller
Mobile gaming has grown on me the best several months thanks to Xbox Game Pass for Android and some stellar controllers like the Razer Kishi and GameSir X2 Bluetooth. These aren't normal controllers through 1 they turn your phone into a Nintendo Switch of sorts. If you want a traditional controller, there's nothing better than the Razer Raiju Mobile, and Amazon is practically giving it away for Prime Day.
Razer Raiju Mobile | $102 off at Amazon
You won't find a better deal on a mobile controller than this. The Razer Raiju is a premium masterpiece, and it's discounted on a steep budget today. Take advantage of its hair trigger controls and extra pack panels to take your gaming to the next level. For just $48, this is an absolute steal.
The Razer Raiju Mobile features as adjustable phone mount, hair trigger mode, mobile app configuration, and remappable back paddles. This is about as premium of a controller as they come. That it's discounted for less than a regular DualSense or Xbox controller is absurd. I really can't recommend this one enough at less than $50. It is by far the best controller deal you'll find today, and I'd wager maybe the best gaming deal entirely, in my opinion.
I think grabbing a mobile controller can help other people get into mobile gaming more, too. Half of the battle of playing a game is being comfortable with its controls. If you're playing with janky touch controls, you won't want to continue no matter how good the game seems to be. Thanks to mobile controllers, I can now enjoy games on mobile that I wouldn't have played otherwise.
Even if you don't play mobile games right now because they don't interest you, I'd remind you of Xbox Game Pass for Android and the growing number of AAA mobile spinoffs like Apex Legends and Valorant. It's no longer just a place where you can play simple games like Flappy Bird.