Judges Boggs, Siler, and Gibbons all agree, for varying reasons, that 18 U.S.C. § 922(g)(4) is unconstitutional. Section (g)(4) is the one that prohibits people who have a prior mental health commitment from possessing firearms. The case is Tyler v. Hillsdale County Sheriff's Department, No. 13-1876. You can read it here. Lyle Denniston over at SCOTUSblog is far more articulate than I and discusses the case here.
While we do not see 922(g)(4) much in practice, the "strict scrutiny" test the Sixth applied to the statute is important and could be used in other gun-related settings.