Lets see, I use on a fairly regular basis:
.jpg, .bmp, .gif, .tiff, .psd, .fla, .avi, .mpeg/mpg, .ppj, .aep, .mov, .midi, .msp, .aiff, .lwo, .lws, .3ds, .max, .html/htm, .txt, .xls, .doc, .ftw, .bak and probably a whole slew of others that Im too tired to think of at the moment.
.jpg (not only because my cam spits them out)
.mp3 (winamp is always active, i re-code a lot too)
.xls (todo lists and calendar that i use almost every day)
.htm and .css (private and professional work)
.tiff and .fh10 (for some of the professional work as graphic designer + scanning)