These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Annoying Arrows: Arrows can come from Archers (duh), Elves, Rangers, Heroes, Towers, Buildings, and even from the sky. Elves and Rangers are by far the worst since they can shoot you from the shadows while being invisible near trees! It gets worse... Arrows can be upgraded into fire arrows, silverthorn arrows, and frost arrows just to make life harder for you on the battlefield.
Best Level Ever: Helm's Deep, Minas Tirith, The Black Gate, Edoras, Isengard (Good side)... The list goes on and on. It's more subjective with the Black Gate & Helm's Deep as they are both well known for being very difficult and frustrating.
Grenade Spam: Later on in the BFME 1 Evil campaign, Gondor constantly spams Trebuchets.
They Changed It, Now It Sucks: Removing Rohan as a faction quickly became this to many since Rohan was a well liked faction and many were annoyed that they just had their Cavalry added to Gondor and a few heroes likewise.
Too Dumb to Live: The 2 horsemen that foolishly gallop into Isengard yelling at Saruman at the first evil campaign quest.
Trade Snark: For some unfathomable reason, the default names for the games' installation folders all have trademark signs in them. Even the Start menu / desktop shortcuts have trademark signs in their names.