Adventure Kid has released a great collection of waveforms for free. You can use these waveforms with synths that can load external waves. With these waves you can make new sounds with your synthesizer.
The saw, triangle, sinus and square (or pulse) are examples of waveforms you can find in most synthesizers. Often these are the only one you can use, but sometimes you can load your own waves.
Examples of synthesizers which can load the Adventure Kid waveforms are Sytrus, Harmless, en 3xOSC van Image Line (FL Studio), Native Instruments Absynth en Reaktor, Camel Audio Alchemy, MetaSynth, Dave Smith Evolver, Symbolic Sound Kyma, Elektron Monomachine en Simpler van Ableton Live.