Flippers that stick out way too prominently when the knife is closed.
Bead-blasted blades.
Overly thick/obtuse blade grinds.
Overly thick handles.
Overly heavy (folders).
Skateboard tape (or whatever it is) inserts.
Made in China. On this point, I will say that I own a few Chinese knives (a Henckels Santoku kitchen knife; a Byrd hawkbill design, and a Messermeister picnic knife) that work very well. In fact, I use the Henckels as my main cooking knife. But for the most part, I do not like "China" on my knives. And I proudly own many knives from Switzerland, Japan, USA, Taiwan, etc. It's probably illogical on my part, but it is what it is.
Serrations that are overly long/pointy/deep, or too fine. I like most Spyderco serrations, but not the ones by Cold Steel or Emerson. And I have one old combo-edge Kershaw with serrations that are so long, narrow and pointy as to be unusable.
Jim