Of course Pixelmator was one of the first to release a Touch Bar update for its Mac image editor. Indeed I think apps like Pixelmator are perfect for the Touch Bar. It gives users quick access to its more powerful features and speeds things up. It makes me wish there was a Touch Bar-based external keyboard for my iMac. This latest update (dubbed 3.6 Cordillera) also includes tabs (a Sierra feature), Smart Refine (which makes selections faster and easier), and Deep Images support.
If you don’t have an image editor at your disposal, I'd recommend checking out Pixelmator. It’s a one-time purchase, as opposed to the subscription-based model, and, as evidenced here, the Pixelmator team is always on top of things. You can learn more at the Pixelmator blog and there’s a cool Touch Bar video below.