1) The Dark Knight
One of my all time favorite movies, I'll never forget the reaction of the audience when The Joker did his pencil trick. Gasps, "oooohhhhhs" then everyone clapped. I love moments like those, even if I barely heard the dialogue that followed.
2) The Avengers
I consider May a "summer" month. I'm in the super small minority that actually likes Age of Ultron better, even with its flaws. But I had so much fun seeing this in theaters, the audience about died when Hulk punched Thor out of frame during the big battle of New York.
3) Dawn of the Planet of the Apes
I love the Planet of the Apes prequels, and I went with this one specifically because of the above gif. Everyone in my theater sounded like they were laughing nervously at this. Like okay, there's an ape, riding a horse shooting machine guns. That's awesome, but kind of terrifying, right? I think Koba may be one of my favorite villains ever.
Bonus: Iron Man, not for my theater's reaction during the film, but during the mid credits scene when Nick Fury showed up. Someone in a perfect Sam Jackson/Dave Chapelle impression yelled out "A MOTHERFUCKING SHARK ATE ME"