Some physical mods:
Spyderco M390/CF Military -- Removed some of the handle to make the full choil useful (not quite finished because I ended up cutting my thumb--not while modding--before finishing it and haven't gotten back to it)
Spyderco Gayle Bradley -- Cut down the handle to show the lock bar
Atlantic Salt -- Cut off the snout, added a swedge, and rounded the top of the hollow grind a bit
Spyderco Pacific Salt -- Charlie Mike'd; first attempt so not pretty, but it works
Kershaw OD-1 -- Slight swedge added just to try my hand at it and I rubbed away some of the bead blast finish to get rid of the rust bucket effect that comes with it
Spyderco Super Blue/Gray G10 -- Aged blue handle coloring
Don't really consider anodizing to be much in the way of customizing, but I've done that to a few, too:
Leatherman Charge TTI -- First time taking apart a Leatherman, and it was a bit of a pain
CRKs of various colors/schemes (Mnandi isn't customized, just snuck into the pic)