I'm shocked and appalled that noone has mentioned the super cheap Arion Tubulator!!!!
The circuit sounds incredible for the $25 price tag. I actually PREFER it to my TS-808 spec modded TS-5. The tubulator has a tad more gain and a smooth smokey OD sound to it that is very very close to the tube screamer, but it's just slightly different. The switches and the knobs on this effect are not first rate and they do go out of order/fall off pretty quickly, but I'd re-case this pedal to keep it running rather than part with it. It's that good. It's tone even impressed Brisk to the point that he was shocked by it's tone and he has incredible taste and supremely nice gear. Incredible tone at a bargain basement price. I'd buy another as a backup, but I just don't feel the need as the price hasn't skyrocketed just yet. For $25, what do you have to lose?