Captain Boomerang will be played by Jai Courtney.
George "Digger" Harkness, aka Captain Boomerang, is an Australian master of boomerangs, which is kind of hard to take seriously. In the comics, he hasn't been the best team player in the Squad.
Jay Hernandez plays El Diablo.
Though there are multiple versions of him in the comics, Hernandez is most likely playing Chato Santana an ex-criminal who becomes a member of the Squad in the New 52 series. He could have pyrokinetic abilities or be a host to a spirit of vengeance. Probably not the latter.
Will Smith is Deadshot.
Aka Floyd Lawton, Deadshot is the most iconic member of the Suicide Squad — especially thanks to that iconic (and faithfully-reproduced!) outfit. The big difference here is under the mask — in the comics, Lawton is white. Smith looks great in the role, though.
One of the more mysterious cast members, Enchantress (Cara Delevinge) doesn't seem to be part of the Suicide Squad team from the trailer.
In fact, in the three brief scenes she appears in, she appears to go from normal woman to insane sorceress — and depending on how close to her comic book roots "Suicide Squad" wants to get, she may become poses sed by a malevolent entity.
Harley Quinn will have her first on-screen, played by Margot Robbie.
Quinn was once Dr. Harleen Quinzell, a psychiatrist that attempted to treat the Joker. He ended up treating her, though — slowly driving her mad to the point where she became obsessed with him and his loyal henchwoman/girlfriend.
Adewale Akinnuoye Agbaje will play Killer Croc.
Born Waylon Jones, a skin condition gave Killer Croc reptilian features that drove him to the sewers and shadows. He's a common criminal — yet a terrifying and strong one.
Joel Kinnaman will take on the role of Rick Flag.
Rick Flag (Joel Kinneman) is the military man who works for Waller and leads the Suicide Squad into the field. It's not a job he wants.
Karen Fukuhara is Katana.
A curious addition to the cast, Tatsu Yamashiro (Katana) is not, in fact, a DC Comics villain, but a hero. We don't yet know why she falls into the Squad's company, but her sword-and-martial-arts skills round out the team nicely.
Adam Beach will play Slipknot.
Probably the most obscure character on this list, Slipknot is an assassin that's really good with ropes. Like, the best. It's weird.