I use the LiveSynth Pro in almost every project. It's very basic -- just a player, not a sampler or editor.

But what it does, it does well, and with very little CPU usage.

Very decent Soundfont/Sample Player. LiveSynth has the best performance (in terms of CPU) than any other sample playback plugin I've tried. So for that reason it's the one I'm primarily using right now. The GUI is a little bare and uninspiring, and it currently has no editing facilities. However combined with CDXtract Multimedia Edition and some high-end AKAI libraries LiveSynth adds serious power to my Sequencer/Studio.