Easy Photo Effects is a basic, but extremely easy to use photo editor which can apply a range of effects to your photos simply by clicking on buttons.
Most of these effects are much the same as you'll see with any other editor. So you can convert an image to black and white, or sepia; adjust the brightness and contrast; add borders to an image, apply an embossed look and so on.
But there are a few which go just a little further. "Movie" adds some grain and borders to create a letterbox effect, for instance. "Analogica" combines a vignette effect with other tweaks to create the look of a picture which has been shot by an analogue camera. And "Tilt Shift" can be particularly interesting, as it's sometimes able to make large objects look like they're tiny toys. This doesn't always work, but check the houses photo on the author's site for a good example.
The down side? The interface is horrible. There are settings for all of the effects, for instance, but they're accessed via multiple separate buttons; a separate settings pane would have been far neater and more usable. And while a progress meter appears to show you what the program is doing, it doesn't disappear when a task is complete: you pointlessly have to click "OK", first. Every. Single. Time.
Still, Easy Photo Effects is free, and tiny (186KB), and portable, and can apply one or two effects which you won't easily find elsewhere. If you want to apply simple, image-wide effects without the hassle of a full-scale image editor then it may be worth a look.