I have an idea. Let's shove all anime together and see what comes up. Yep... Demon Butlers taking down demon titans... while Orion is being chased by Lucifer... Sailor Moon and Rize are conspiring... Santana and Genoa have teamed up with Naruto and Sasuke... and Ash is still 10...

Okay, that's not a great idea. But crossovers would be awesome none the same.

The one I'd most like to see is Attack on Titan X Fullmetal Alchemist

With two hotheaded protagonist, a sibling who is badass yet quiet, the badass older male character, the smart blonde character, the wacky friend, and an outside force to worry about, these two would go along perfectly. While it's debatable whether alchemy is more efficient for defeating Titans or Edward Elric would beat Eren Jaëger in a fight, this would be a crossover I would pay money to see.

(sorry for the quality)

Honourable Mentions:

Attack on Titan X Black Butler

Attack on Titan X Death Note (lots of AoT)

Black Butler X Pokemón (I never knew I needed this until I saw this picture)

Credit to the amazing artists and memer:
1. [Comment if you know them!]
2. [Comment if you know them!]
3. Pondana on tumblr
4. rikugame27
5. [Comment if you know them!]