best ab workout dvds?

I have to stregthen my core muscles and wanted to know the best dvd to get?

suggestions?

thank you

Best core-specific execise: Planks, side planks, rollups, pushups, bird dogs, prone bridges, single-leg glute bridges, Pallof presses, wood chops, medicine ball slams.

 Do you have any specific reason for wanting to develop core strength? It's often the case that for sports-specific training your exercise selection will be a bit different than for general health/fitness goals.

Tony Horton's AB Ripper X.  Man it's intense, but awesome.  "I hate it, but I love it."

30 day shred! Started with 3 lb weights, and as I increasing weights it keeps staying intense.