I found sonigen being extremely powerful VST tool. I is an extremely powerful synthesizer with almost infinite possibility. You could use it to recreate many classic sounds using the built in modules. It includes hundreds of built-in presets and incorporates a pleasant experience and is a very user friendly synthesizer. OF course, you could easily lose yourself in the creative aspect and easily make a synthesizer that looks like a giant bowl of spaghetti.
It also has a unique sound that is all it's own, bringing it's own unique twist to bear. You will not ever regret downloading this. If it wasn't free it would be well worth every penny spent on it. But it is, and it is well worth the download. It is a lean, mean,synthesizing machine.