"Gangsta" definitely. It's actually one of my favorite Manga series' right now apart from "Vagabond" so I hold it in very high regard. I'd even say give the "Terra Formars" Manga a try. I was left with a bit of a bad taste in my mouth after the Anime but the Manga helps to wash that away. I'd say the exact same thing for "World Trigger" too.
Having taken Frank's advice to pick up the first volume of Gangsta, I'd agree with checking that one out. It's something I never would have picked up if I was browsing, but the first volume has intrigued me and I look forward to reading the second on the weekend (after I get done with my wonderful Seki-kun which I love so much but not sure how it would go for anyone who hasn't seen the anime -side note: I *HIGHLY* recommend checking that out).
I just thought I'd add a little extra in here and list what I'm enjoying. I tend to get distracted with my manga, so I've started a lot but am up to date/finished with few! Not sure you'll find much here that you don't already know Luke, I mostly read shoujo romance stuff!
But my favourites & best of what I'm currently reading:
- Kamisama Kiss - High School Debut - Tonari no Seki-kun - Grand Guignol Orchestra - Terra Formars - Seraph of the End - Kimi ni Todoke - Inu x Boku SS - We Were There - Your and My Secret - Watamote
And having just finished the anime over the weekend, I plan to start reading Akame ga Kill as soon as I have some spare money to pick up the first volume. I've heard from people of some major changes from the anime (one of my favourites is still alive in the manga) - not sure if the manga will be different or is just still working to the same point but I loved the anime and I think the manga could be really amazing.
From what I've heard about the "Akame Ga Kill" Manga, it's so much better than the Anime. Which is great because I already thought the Anime was pretty good. Can't imagine just how much better the Manga must be put it's pretty damn exciting. I love a nice, long Manga list. What I'm currently reading is "Vagabond", "Gangsta", "Terra Formars", "World Trigger" and very soon I'll be reading "Assassination Classroom".
If you're looking for some mindless fun that is super cute, then check out Donyatsu. I found the anime shorts on Crunchyroll and then heard recently they've got the manga now too. Read the first volume yesterday and I totally love it