My personal TF2 pet peeves have already been said, but here's one I personally have that some may or may not have: fluctuating item prices. For those of you who may not know what I'm talking about, it goes something like this: You trade almost half of your inventory for a really valuable item, whether it would be a cosmetic or a strange weapon. You finally sacrifice enough of your favorite weapons and items, but in the end, you've obtained a very good item, for the day at least. You go to the same or a different trade server a few days later and hope to trade away your cosmetic only to realize that your once valuable item has turned into a piece of garbage. Goodbye weeks of earning and trading. This really infuriates me.
Another thing that peeves me that I think also applies to a lot of players is crap ton of crates, but NO KEYS!!!!!!!!
One last one that I have is the stupid "updates" made to the game itself. Whether it be skinned items or inspection animations, nothing really has changed. The only significant changes I've seen recently were from the End of the Line update: new weapons, a new and interesting game mode which is almost like payload with a twist, and a new TF2 animation that came with the update.
If anyone else relates to this, then brohoof to you.