Best 303 screamer?

Try to find a Acid Screamer…one of the best i could find in combo with a 303!

The RAT is great on a real 808 I must say.[/quote]
The RAT is good regardless, use it alot with synths.

I have one of these really good you have a bit of control of which frequency you want to effect. Not available any more, but I contacted the builder last year and he has said he is working on another version. You need to go on a waiting list with a promise not to contact him or he will take you off the it. LINK

The RAT is great on a real 808 I must say.[/quote]
The RAT is good regardless, use it alot with synths.
[/quote]
Only used it on drums myself - used to be great with the old XD-5 (Kawai Drum rack) I used to own also.
The closest I get to 303 these days is either the A4 or a TB3 (which oddly enough sounds great fed through Logic’s Bass Amp Simulator (the new one in Logic X).
I have really crappy Behringer Bass V-Amp which sounds very average with a bass guitar but quite good when you feed synths through it.
I’ve been known to feed MnM SID bass sounds into it and then filter the output through the A4 to good effect.
I also swear by certain effects on the older BOSS SE50 and SE70 (half sized rack units) - some super grungy tape delay simulations to be found that are superb at adding lo-fi grit to a signal.