UVI Falcon - Sampler/synth hybrid instrument
Revoice Pro - Revoice Pro is an audio plugin used for vocal tuning, time correction and ADR.
Pianoteq - Pianoteq is a virtual piano that runs on your computer.
GSnap - With GSnap you can get an auto-tune effect.
LinuxSampler - LinuxSampler - free, open source pure software audio sampler with professional grade features.
MOTU MachFive - The universal sampler for creative music production.