Here is an updated answer as of August 2014 for some that are aimed or work well with Scala.
Personally I think the JVM or Java ones end up with far too many false positives, or have inspections that are aimed mostly at Java specific classes. For example, since in Scala we don’t tend to use the Java Collections, all the findbugs collection based inspections are not needed. Another example is the inspections for use of static fields which are irrelevant in Scala.
- Scalastyle https://github.com/scalastyle/scalastyle
- Scapegoat https://github.com/sksamuel/scalac-scapegoat-plugin
- Wart remover https://github.com/typelevel/wartremover
- Linter https://github.com/HairyFotr/linter
- CPD https://github.com/sbt/cpd4sbt
- Abide https://github.com/scala/scala-abide
- Codacy-scalameta https://github.com/codacy/codacy-scalameta