WildBit Viewer is a photo viewer with support for a wide range of formats. It has all the functionality you could expect from such a program although there are a few extras that make this stand out.
Firstly, WildBit Viewer is very fast at reading the contents of directories of images and displaying them as custom sized thumbnails in its interface.
But above all, the slide show feature lets you comfortably see your pictures without having to click through them one by one. Select from a few options and display your pictures on a full-screen with over 150 transition effects.