Using sine and pushing it through bags of distortion is great (almost resembles a square wave, but sounds phatter due to the transient-like distortions). Due to it then having more harmonic content to play with, you can then mess around with the filters + resonance to fine tune it. Square-esque type waves are just evil, mwhahahahaa

Using two similar oscillators is good, but use very small amounts of detune only otherwise the waveform will start 'beating' (kinda like, er, flapping about a lot, lol

). Adding a very small amount of ring-mod will also add some nice dirty harmonics when used on two sine oscs.
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Timo proceeds to stick Spin Spin Sugar on, on the hifi]