I'll start it off with this:
Hataraku Maou-sama is a series that really stood out for me last year. for a 13 episode series it was pretty freakin solid imo.
and since Funimation has been dubbing this series lately I've decided to give it a 2nd watch with the funimation dubs, 2 episodes in and I'm still enjoying it as much as I did when it first came out. (Yeah I like dubs... but some dubs... mainly Funimation's dubs... sue me).
So yeah, on the top of my head, that's the first of many Animes I think deserves a 2nd season.
What other animes do you think deserves a 2nd season? & please don't flood this topic with a bunch of lists.
just go with the 1 on top of your head.