I'll list some good ones I've watched, I'm specifically putting down animes with 12-30 episodes (with the exception of Brotherhood since its amazing) that have complete story lines, I don't want to leave you on an anime with a cliffhanger that will be resolved in 2017.
Full Metal Alchemist: Brotherhood,
64 Episodes, but it's goddamn worth it. Make sure its Brotherhood though, not the other version.
Steins;Gate,
24 Episodes, Delusional scientist accidentally makes a microwave that can send messages back in time.
Cowboy Bebop,
26 Episodes, Bounty Hunter / Space Cowboy, cult classic, definitely worth a watch.
One Punch Man,
12 Episodes (Currently Airing), Guy looking for tough people to fight, his only problem, he can defeat everyone with a single punch.
Parasite: The Maxim,
24 Episodes, Guy wakes up one morning with an alien parasite living in his hand.
Psycho-Pass,
22 Episodes (Season 1, but a complete story. Not watched Season 2 yet). Dystopian future where it's almost pre-determined who is going to be a criminal.
Samurai Champloo,
26 Episodes, 3 strangers meet and end up travelling to find a samurai who smells of sunflowers. (Lame description but it's really really good).
Ghost in the Shell: Stand Alone Complex,
26 Episodes, Elite Police Unit tracking down a Mysterious Hacker Criminal.
Beserk,
25 Episodes, Much Darker, Adult anime, follow the story of Guts, a young powerful mercenary that teams up with a mysterious bandit leader.
Black Lagoon,
24 Episodes (2 series), an office worker gets held for ransom and eventually starts working with a group of mercenaries who took him.
Darker than Black,
24 Episodes (First series only), Mysterious gate appears, and people called Contractors gain super powers. (Lame Desc, but quite good).