For me, brass on new knife is like poison-I prefer stainless or bronze. I don't care for giraffe bone, mosaic pins, excessive number of pins or too much epoxy repair on a wood handle.
I despise pakkawood, miraclewood, wildwood or whatever you want to call it.
Plywood is good for hockeysticks, thats about it.
There is room for a bead blasted finish on certain knives, but I would greatly prefer a finish like gunkote or hard chrome after blasting. I could never keep my bead blasted stainless microtechs free of rust.
Most makers make handles too short, too flat and too small. I have pretty large hands, but a handle can generally be smaller, its hard to go the other way.
I stopped collecting folders about 5 years ago, so my comments really just apply to fixed blades.
The #1 deal breaker for me is poor design. I have seen some really nicely made knives that exhibit really poor design. In my opinion, about 75% of handmade fixed blade knives I examine at shows exhibit design issues of some sort.
Tactical "combat style" knives should be non-slip, have a thonghole, and at a minimum all areas not covered by the sheath should be non-reflective. The sheath should be synthetic, sturdy and able to be compatible with webgear. I think a Mad Dog ATAK is a good example of what a tactical fixed blade should look like.
Hunting knives should have a thonghole,IMO and a functional integral or attached guard and exhibit excellent edge geometry. .250" stock is a poor choice for a 3.5" hunting knife

. The handle should be shaped or contoured to be non-slip. Hunting knives should be gap-free or they will most certainly rust under the scales regardless of the steel used (unless its non ferrous). I like Jason Knight and Adam Desrosier hunters. I also like hunters with stag. It is pretty, non-slip, and fits the theme.
Reproductions should be reproductions. Making a replica of a 150 year old knife and then adding a mosaic pin or using materials not in use at the time just doesn't work for me.