Agree with the hotspots. Contego is a great example of designers obviously not handling a knife much without gloves.
For me, the biggest pet peeve is a production or "mid-tech" that is well beyond the price tag it deserves whether it be because of name, fit and finish, looks, what have you. Nothing worse than seeing a $200 liner lock that develops bladeplay, or a $300-$1000 mid-tech with old technology, outdated materials, or issues with bladeplay/other design flaws. Not when there are literally hundreds of knives at a fraction of the price that more than meet the standard.
One more would be subhilts and finger grooves. Dude, not everyone has the same hand size, so why do some makers turn out knives for gorilla mitts? Maybe people have large hands but like smaller handles, or have medium to small hands as it seems like a lot of knife guys do? Or what if a woman wants to enjoy a gigantic fixed blade but can't because "I've got these tiny hands"?! Just a thought.