Deadshot (1988 mini-series) - This mini-series set before The New 52 reboot shows off the insane side of Deadshot, his ties to his family, and even shows that he does have a heart. I will also say that this mini-series even deals with child molestation and is also violent so if you're squeamish when it comes to that kind of stuff then skip this. The mini-series has also been re-printed along with some other Batman and Detective Comics issues featuring Deadshot in a graphic novel called: "Deadshot: Beginnings".
Suicide Squad by John Ostrander - This series also shows him as a prominent member of the team and it has some cool moments featuring him interacting with the team. It also has cool action scenes with him.
Gail Simone's Secret Six and Villains United - Gail Simone had Deadshot as a prominent member of the Secret Six before the New 52 reboot and it does have some funny moments with him and the team at times. Like I said about his appearance in John Ostrander's work on the Suicide Squad series from the 80's, the series does have some cool action scenes featuring him.