IrfanView is a very powerful graphics viewer and converter. It supports the following formats:
AIF, ANI/CUR, ASF, AU/SND, AVI, B3D, BMP/DIB, CAM (Casio JPG), CLP, Dicom/ACR, DJVU, ECW, EMF/WMF, EPS, FlashPix (FPX), FSH, G3, GIF (including animated), ICO/ICL/EXE/DLL, IFF/LBM, IMG (GEM), JPG2000, JPG, KDC, LDF, LWF, MED, MID/RMI, MNG/JNG, MOV, MP3, MPG, MrSID, NLM/NOL/NGG, OGG, PBM/PGM/PPM, PCX/DCX, PhotoCD, PNG, PSD, PSP, RAS/SUN, RAW, Real Audio (RA), RLE, SFF, SFW, SGI/RGB, SWF (Flash/Shockwave), TGA, TIF, TTF, TXT, WAD, WAV, WBMP, WBZ/WBC, XBM, XPM, CRW, NEF, ORF, RAF, MRW, DCR.
IrfanView also can be used to capture scanners, Slideshow, saving the result later in an .exe, Batch conversion and many more utilities that possibly make it the best.