Hate/tired of:
Chisel ground tantos - unless you're professional carpenter or wood carver it's totally useless blade shape and grind.
Custom pivot screws that need special keys.
Thick heavy tactical bricks or sharpened pry bars.
Organic blade shapes with blunt noses, they can't cut or stab!
Organic/architectural post modern/sci-fi handles that are not designed to be used by bare hand for more than 1 minute.
Knives designed by marketing/accounting department not by actual users.
Glass breakers, belt cutters, and other bell and whistles that only belong on emergency rescue or multi-tool knives, not on regular folders.
Short blade long 2 handed handles on folders, looks stupid, makes difficult grip changes and too little cutting edge. Nobody evers says "I wish I had shorter cutting blade with longer handle!"
Good folder should be 50/50 blade to handle and fixed small-medium size blades should be 60/40 or 70/30 unless its a broad sword it doesn't need super long handles.
Fixed one handed blades should have handles between 4-5 inches.
The Worst feature:
Finger choils on the blade are waste of valuable, usable cutting edge on small 2-3 inch or big 12-36 inch knives don't need them, in fact no knives needs them. They look ridiculous, like balls on grandma! If you need to do fine detail point work that is why you use small folder or multi-tool they are perfect for that kind of work.
"Right tool for the right job!" otherwise you end up with mediocre tool that is not good at anything except being expensive paper weight ex: chisel ground tanto shaped pry bars or blunt nosed straight edge sheepsfoot/wharncliffe, broken back seax etc.
The Most Hideous feature:
2 inch blade with 1 inch finger choil and 7 inch handle!!!!