Image Line has released Toxic III for Mac OS X. It is available as a VSTi and is a Universal Binary, compatible with both PPC and Intel Macs.
Toxic III currently costs $59. A demo version is available. Current Toxic III owners can obtain their free OSX Serial Number from their "My FL Studio" page.
Toxic III features a hybrid synthesis engine, combining the best of FM and Subtractive synthesis. More info here.