for me at least, i like the two extremes as far as color goes.
i love dark wood or horn, finished to a high gloss and with fittings of either wrought iron or silver. the silver provides a good contrast with the dark. very classy to me.
i also really like a light wood like maple, myrtle, or birch with either bronze or brass fittings. i like the colored fittings with the lighter wood because they accentuate the yellow and orange tints in the wood.
shape wise, i'm a big fan of flowing, organic looking handles. any work by Gerhard Wieland is a perfect example of this. if it has a guard, i like it to be understated, contoured, not overpowering or unbalanced. usually accentuated by a groove running through it to add the illusion of slimness. for fighting knives, i like the handle shape with a slightly larger butt end than ferrule end. usually with a palm swell.