The Wacker-Arena is Burghausen's football stadium and the home ground of SV Wacker Burghausen. It sits in the newer part of town rather than the historic centre, so it is not a sightseeing priority unless there is a match on.
For football-minded travellers, though, it offers a different angle on Burghausen: this is an industrial border town as well as a castle town, and the club is tied to the large Wacker chemical works that shaped modern Burghausen. Check fixtures before making the trip; otherwise your time is better spent on the ridge and in the old town.