Gutterballs (2008)

This is almost the definition of "uneven." The soundtrack is terrific and the gore is much better than anyone would expect for the budget, but the film goes out of its way to be offensive in ways it doesn't need to be. The black guy isn't the first killed and there's a transsexual character that is treated well by the film (until a horrific scene best not described here). Then there's a rape with a bowling pin. There's a rape played for laughs. There's a clever twist with the killers, though it's been done before and you can figure it out if you cared enough. Some of the film is quite bad, some effective, but mostly it's scattershot.

Added: I didn't adequately describe how offensive this film is. It's offensive. It also had a sequel.