As far as superheroes go, first you'll need to decide between the DC comics heroes or the Marvel Heroes. For those who love DC, the grouping with Batman, Robin, Superman and the rest of the Justice League. For Marvel fans, go with the Avengers including Captain America, Iron Man, Spider-man, Thor and Wolverine.

Transformers are another popular one. While Optimus Prime may be the leader of the Transformers, most kids gravitate towards their own favorite from the likes of Bumblebee to the bad guy, Megatron. Every Transformer has his own personality and style, and when buying boys group costumes it should be easy for the kids to pick which one to be.

Outside of the great superhero costumes out there, you also have the classic group costumes: pirates, cowboys and indians, cops and robbers, an Halloween ghouls. The upside to these boy's group Halloween costumes is that they're a little less character specific, so there's no fighting over who gets to be what. Everyone in the group will be happy.