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.
Crowning Moment of Funny: Michael, after giving several characters a crash-course in automatic weapons usage, says if they get it wrong it might blow their hand off. Cue everyone looking at Percy, former military man, and his hook for a hand.
Percy: "What the fuck ya'll lookin' at me for?"
There's also the scene near the end where Audrey tries to shoot Gabriel in the face with a flare gun. She misses, but the flare bounces around for a bit, and hits Gabriel anyway.
Genius Bonus: Michael going against God (and thus being called "rebel son" by Gabriel), in some countries Christianity got a bit muddled and so there are places where Michael is the one cast from heaven for mutiny.
Michael is actually the angel usually used for doling out God's judgment in the Bible, while Gabriel is usually the angel that is the deliverer of good news, (i.e, the message to the virgin Mary, etc.) so if you know those traits, the movie has a special ironic streak to it.
Narm: The whole damn film is filled with Narm and Narm Charm to the brim. Moviegoers went into hysterics after watching the trailer featuring that possessed old lady climbs up onto the ceiling. The whole scene with the granny qualifies, really. Hearing an old lady say "You and your fucking baby are going to burn" is hilarious, not scary. There's also the Creepy Child ("I just want to play with your baby") and Gabriel's chainsaw-mace.
One-Scene Wonder: Everyone can agree that the possessed granny is probably the best part of this film.
Ships That Pass in the Night: Audrey/Gabriel is rather popular on Fanfiction.net and DeviantArt. This despite the fact that the two share exactly one scene, where she tries to strangle him and they both go through the windshield of a car at 90 miles an hour. Being an archangel, he lives. She...doesn't. It's nevertheless one of the most popular Het pairings in the fandom on both sites.