PhotoMania is a free photo editor. No registration is required for online use. The app can be downloaded for use on Android and iOS moblile phones.
The editor stands out for its ease of use. Regulate the intensity of effects by using a slider. On the downside, applying one of the wide variety of effects will reduce image resolution; also, the image is watermarked.
Here’s a sample:
The first image is the original, the second shows Photomania’s watercolor effect and watermark.