ok, i have plenty of things which grind my gears @ HHN.
To start, the moronic parents who bring their small children into the park thinking, it's some sort of like a "slightly scary halloween party", but the reality is that this is beyond the fear which is seen in many Disney movies, this is universal meaning that it is bound to be a bit between PG-13 and R. and if you're not careful about bringing them and using common discretion, don't be surprised if you have to spend your savings on therapy bills after your kids end up traumatized due to the blood and gore in HHN.
Second thing are smokers. Not only does it annoy others, but on a blustery day, a puff of smoke can sour everyone else's experience.
The final thing is anything that lights up. Not only does it blind others including scareactors (especially during the day when it leads for a house to be pitch black), but it kills the surprise element. that's why i never bring anything that lights up (including my mouse ears which i often wear for mardi gras)