It might be a little grim to imagine Pokemon in the world of Attack on Titan, but, hey! Titans only eat humans, remember? That said, if for some reason the worlds collided, Goldfinch figures these would be the pairings we'd see.
What do you think, who would you pair up? I'd probably put Eren with a Pokemon that knew self-destruct, but man if that Levi pairing isn't kind of perfect. Here are some more:
進撃のポケモントレーナー [Goldfinch via Soldadito]