4) Pigtronix Rototron
What's that you say?! Leslie speaker emulation that actually sounds like a Leslie speaker?
It combines a number of effects, including delay, brigade-based chorus, tremolo and frequency modulation to nail the signature Leslie wail.
It's about more than just trying to make your guitar sound like an organ, it adds life to chords and rhythm playing, with constant fluctuations and modulation.
It just makes your guitar sing that little bit more, or if you want it to, it can make it scream.
If you DO want your guitar to sound like an organ, then combine the Rototron with an EHX POG and you've got a tone sent from the heavens.