Sure, there are plenty of ways to play NES games on the go, but most of them don’t take actual cartridges. The Retro Mini Handheld NES System ($50) is like the Game Boy that never was, with a 2.4-inch LCD screen, a top-loading slot for NES titles, AV output, built-in speakers, a headphone jack, and the ability to run up to eight hours on 4 AA’s.