Buzz is a tracker that also offers support for both VST plugins and plugins in its own format. It has been updated many times in recent years and now support multiple cores, 24-bit 96 kHz audio, reads .wav, aiff, flac, ogg and mp3 files, offers per-machine oversampling, preset morphing and randomization of any plug-ins (VST or internal) and much more. Buzz has been the inspiration for countless "buzz clones", but the original remains on top IMHO.
What I really appreciate about it, is the user interface. It is not that easy to get to learn, but once you know the hotkeys, creating new tracks is blazingly fast as we know it from trackers in general. Here are few relevant links: