Today, I'm recommending Sakamoto Days by Suzuki Yuuto.
This manga is quite possibly one of the coolest new shonen coming out. We have retired hitman Taro Sakamoto, who before retiring was probably the greatest hitman ever, and since retiring he's put on a hefty bit of weight and has chilled out, owning a convenience store with his family. All of a sudden though, the underworld sends an invitation to Sakamoto, inviting him back into the fray.
Highly recommend, and the fact that there isn't an anime announced for this series yet is highly criminal.