I think one of the most bizarre genres is "crabcore", but not for the reasons UG.com gave. When I listened to an Attack Attack song, it was a weird mix of metalcore, electronic dance music, soppy rock balladry, screamo vocals, autotune... such a weird combination of styles. Whereas something like Blackened Death Metal is a fairly straight-forward blending of death metal and black metal, two already relatively interlinked subgenres. Maybe I am missing the point here, but in reality a band like Behemoth is hardly anywhere near as bizarre as a band like Attack Attack.