In readily available, affordable phasers that don't take up a lot of pedalboard realestate its a simple choice between the phase 90 and small stone. They are both voiced very differently and use a very different circuit to achieve their phasing. I am more of a small stone guy, but the mxr will suit more people. EHX recently rereleased the classic bad stone phaser. Its less extreme than the small stone and has more controls but its bigger. MXR also does the phase 100 that is to the phase 90 what the bad stone is to the small stone; less stages of phasing with more knobs. The old DOD phasers are real sleepers and can be had for reasonable prices. They are FET based designs like the EHX phasers but have more of the MXR voicing with a narrower, guitar-centric bandwidth and real focus.
The best phasers I have ever played were vintage mu-trons, but they are pricey (especially the notorious bi-phase) and they have shitty, tone-eating bypass. But they have a glorious, warm phase sound that cannot be set to sound bad even if you turn the knobs until they sound a little silly. The circuit for mu-trons phase is just phenomenal. Sadly, if it breaks (and they break, they are OLD) you are up shits creek as they are full of parts that have been out of production for decades.... and those parts are part of the great tone. 2nd runner up is the old Maestro phaser, I think there are some boutique guys cloning this.
Another different option that's not exactly a phase are the pedals absed on Fender's Brownface harmonic vibrato. This effect is not true pitch vibrato but is a weird mix of tremolo and phase that effects treble and bass frequencies differently. In the Brown and Blonde fender 6L6 amps this effect was achieved with a pile of 12ax7 tubes (much like Magnatone and Vox true pitch vibrato on the vintage amps). Catalinbread and EQD clone it in pedal format with fets and the CB version, the pareidiola, sounds awesome. I haven't tried the EQD harmonic vibrato yet because it was just released at NAMM.
Keeley's phaser has a devoted following too, but I haven't tried it...
the fulldrive is a tubescreamer... its a little more hifi and achieves the TS signature feedback loop clipping with those mosfets wired as diodes which yield a less compressed sound. I had one briefly. It was just okay. Sits pretty squarely in the TS9/SD1 camp and costs an arm and a leg. If you prefer fender blackface amps you may like it more than a stock TS9 or 808. If you play british amps look at something that leans closer to Boss' take on the TS9 type OD (the SD1). The MXR custom badass m77 OD or whatever they call it with the gold box? Good place to start if you have a vox or marshall. In the diodes-to-ground camp there is always the classic OD250 or the EHX soulfood (which captures the klon sound pretty darn well for very little money). then there are the amp-in-a-box drives and there's a lot to say there. I have owned some and tried a lot. I tend to like the Catalinbread versions, especially into blackface fender amps. Bogner's Ecstacy Blue pedals is also fabulous. I am interested to try his pedals with little output transformers, but I never seem to make it out guitar shopping lately.... all that said, if you want a pedal that sounds like a cranked amp nothing gets you there. Lots of things add the falvor of a certain amp or style of amp, but a pedal just doesn't have the goods, particularly into a clean amp.