When you don't have an actual bass and use your regular guitar?
 
I've tried using a pitch shift pedal in Amplitube 3 & 4......A4's pitch shift pedal didn't work as well as the one in A3. It wasn't too bad, but wondered if there's a better way to use them. I also have Jam Origin's midi guitar.
 
Just wondered what you guys use that works pretty well?
 
 

I have used the BOSS COSM octave transposition effect (in my BR-600) in the past.  It works fairly well except if you hold a note for a long period of time.  When the signal decays, its gets a little wonky.

Synth bass played on my keyboard (if Bapu's not available..which hasn't happened  often..) Never had any luck simulating a bass using a guitar, I've tried several methods, including converting audio to MIDI.

Mesh
When you don't have an actual bass and use your regular guitar?
 
I've tried using a pitch shift pedal in Amplitube 3 & 4......A4's pitch shift pedal didn't work as well as the one in A3. It wasn't too bad, but wondered if there's a better way to use them. I also have Jam Origin's midi guitar.
 
Just wondered what you guys use that works pretty well?
 
 

If you wanted to take, say Joan Baez's voice and turn it into Barry White's, what would you use?
 
I'd assume if it worked "pretty well" for that then it might work "pretty well" for what you want as well.
 
And vice versa 

Keyboard

I use the SI Bass synth, and then run it through an amp sim (AmpegSVX for me).
It's not as good as a real bass, but might be better than re-pitching a guitar.

VSTi->amp sim chain as well, more for convenience. The nuances of a real bass do not pitch shift well from a guitar, so a real (cheap) bass would be a better route.

There was a decent post regarding this while back but forgot what method he used. Melodyne in melodic mode may be another option to try.

A VST - usually DimPro - but quite fancy one of these: www.theguitarmagazine.com/gear/bass-guitars/taylor-gs-mini-e-bass/

I drop my guitar down an octave using sonar's pitchshift algo, then I put that through a bass amp. I find this works better than using midi because nuances still come through. Slap bass doesn't work to well using this method. Here is a video I did demoing this method.

https://youtu.be/_iJlTc_qdrQ

double