This challenge includes the Pre-Avengers movies too :)
Day 1: Favorite Pre-Avengers Movie
Day 2: Favorite Avenger
Day 3: Least Favorite Avenger
Day 4: Favorite Non-Avenger
Day 5: Favorite Villain
Day 6: Favorite Fight Scene
Day 7: Favorite Official Art 
Day 8: Favorite Fan Art 
Day 9: Favorite Avengers Merchandise
Day 10: Underrated Character
Day 11: Overrated Character
Day 12: Favorite Animated Gif
Day 13: Favorite Location
Day 14: Saddest Moment
Day 15: Favorite Pairing
Day 16: Marvel Character You Wish Was Included
Day 17: Favorite Poster
Day 18: Favorite Quote
Day 19: Funniest Quote
Day 20: Favorite Eyes
Day 21: Favorite Actor
Day 22: Favorite Name
Day 23: Power You Wish You Had
Day 24: Favorite Costume
Day 25: Favorite Weapon
Day 26: Funniest Moment
Day 27: Movie With the Best Soundtrack
Day 28: Character You're Most Like
Day 29: Saddest Character Death
Day 30: Favorite Moment

Day 1 is June 1 of course ;)