The Tweakbench Nintendo plugins are awesome for producers just starting out. I used it a lot before I got Super Audio Cart. Not a lot of depth but very simple and it doesn't take that long to get sounds you want. Triforce has your square, saw, and triangle waves and offers a bit of manipulation; Peach has random sounds from various NES games, which is fun to play around with; and Toad is a drumkit. If you're into 8-bit music or like having a retro sound, those plugins are the way to go!
You can download the bundle for $5 if you want to support the dev that made the vsts, or you can download each individually for free.
Did I mention that it's free?