i think this is a question everyone would like to know really.

The best ive done my self is via a square wave with the filter attack being ramped up via the adsr. This does your basic 'wap' type noise an early example is http://www.fuktstereo.com/dont-stop.zip its about 1.25mb unfortunately. this is a tune i stared working on and then stopped for the moment. It is really really basic and no where finished and recorded @ a very lo bitrate but the bass uses the above method.

Another good way is to create a gabba kick via distortion then reverse it. The problem is that it is not - musically pitched but you can find common harmonics so that it will fit with the rest of your music.

I see that you use the virus - pretty much all producers have one in their sutdio - its is the one to use really, that and the nord which wavetraxx said scot project uses for his basses.

Jungalist is another good instrument to use - guyver uses it on his productions and it does a wicked arome double off beat bass noise.

I hope this helps a little,but it this really is the $64,000 question.

Hopefully i will be able to find this out in the future.