Honeyview is a portable free image viewer from Bandisoft, the developer behind archiving tool Bandizip.
File format support is excellent. Honeyview opens regular formats including BMP, JPG, GIF, PNG, PSD, DDS, JXR, WebP, J2K, JP2, TGA, TIFF, PCX, PNM, and PPM, as well as all the main RAW formats (DNG, CR2, CRW, NEF, NRW, ORF, RW2, PEF, SR2, and RAF).
The program has also borrowed a little code from Bandizip, which means it's able to directly view pictures inside archive formats including ZIP, RAR, 7Z, LZH, TAR, ALZ, and EGG.
Whatever you're browsing, Honeyview provides many navigation options. You can move one image forward (or back) by spinning the mouse wheel, clicking Back/ Next buttons or using the arrow keys; Ctrl+PgUp or Ctrl+PgDn jumps forward or back by 10 images; a scroll bar allows you to jump straight to some preferred position (image 31/44); the Home/ End keys go straight to the first or last image; or one click opens a thumbnail browser to help you find the photo you need.
The core image viewer is impressive, too, with a host of zoom controls, optional EXIF tag display, bookmarking, slideshow support (including transitions) and simple editing tools (resize, rotate). It also has plenty of image processing options - soften, sharpen, flip, gamma compensation, various interpolation types - yet still remains very fast.
There's support for viewing the location of GPS-tagged photos on Google Maps.
Honeyview also provides a "Photo Folder" option where you can store any interesting photos. Set this up to point at whatever folder you like, then start browsing as normal, press Ins when you spot a photo you need, and it's copied to the Photo Folder. A Ctrl+Ins function alternatively moves images to the Photo Folder, and both options can make it easier to sort your pictures.