Alesis Quad/quad +/Quad GT- Amazing textural reverb. Good reverb chorus, good delays. Some OK modulations. The rotary speaker on the quad gt is nice. Bad side is global preamps on the quad GT you can;t bypass and the noise level is really high
Alesis Microverb/Midiverb-Offer even more reverb then the quad. Unit overload and distort in a very nice way. Again, noise is the drawback.
Boss SE-50/70 - Good reverbs. They can overlaod the unit at higher mix levels turning it into a distorted mess. The noise is almost 0 off these units. I use a SE-50 now(used to be a quad GT)
Zoom 507 reverb - good basic verb. Cheap as hell. No noise. Drawback is that the construction some people dislike. It is fine(I dig with one as my second reverb).
Boss RV series of pedal - I really dislike all of these. Best is the RV-2 and it is really noisey. the RV-3/5 are both cold and lifeless IMO.
Digitech Digiverb - Some really nice sound out of this. Really massive reverbs, issues is a batery last 10 minutes in it. And the reverse isn;t really all that hot.
Electro Harmonix Holy grail/holier grail-I really like the holy grail, but teh one I had was defective. The holier grail can be annoying as well(that much control should be foundd in a rack and not a pedal IMO). Do not buy these off ebay.
Korg DRV-1000 - My next reverb unit. Low noise, huge reverb times, a good reverse and knob! Problems are they are hard to find.
Boss RRV-10 rack - Not much info, if it sounds like a SE-50 and has low noise it will be in my rig as well.
Digitech XP400-Really bad. High Noise. Lame reverbs.
Lexicon units - Not much experence with them. Are teh standard for reverb in the recording world. Most are too high-fi for amboient(lower bit rate reverbs work better then newer stuff)
Digitech racks - neither here nor there. they work. Nothing more.
A good analog delay should be in any ambient rig. Be is a Ibanez Ad-9, Boss DM-2, or even DOD's, raks, almost anything with 300-450 ms of delay that self oscillates.
Or you can use a good analog sim, liek a DL-4, or a DE-7(my favourite)
For digital delays, you should have at least 2. One can be anything with 800ms plus delay. The other shuld be a looper, with at least 4 second of sample time. DOD FX94, Digitech Digidelay, DL4, DD-20,DD-6, akai headrush, or a dedicated looper like a RC-20. The digitech GNX3 is a good multieffect for ambient because of th built in looping and ability to use the built in effect with the external switch($30 extra).
Other loopers include non static loopers, liek the PDS seres(tweaked for more time) by digitech. These work by setting the delays time, recroding it till it is layered, and putting on the repeat/hold. These are the best for recording drones. Maneco makes beautiful modern version of this type of looper. The Digitech PDS1002, 2000, and 20/20 are all cheap(by far teh 20/20 is best because ith a simple tweak you can get 20 seconds of delay out of it)
PitchShifter-the boss Ps-2 is the slowdive pedal. I am not a huge fan of this box except as a delay. The boss PS-3 is AMAZING and should be on any ambient board. The digitech spacestation is anotehr one people like for string sounds. The PS-5 is a good pitchshift as well, but is missing a few of the modes from the PS-3 that make it my number one pitchshifter. the old ibanez harmonics delays are great for lowfi pitchshifting.
Phasers-Electro harmonix small stone is the best mass produced phaser for this type of music. MXR phase 100(re-issue or not) is second. These both havea wicked "airy" sweep and add pile of texture to a sound. Vintage choices are many, the old morely is what nobody(another ambeint guitarist on this board) swears by. Mu-tron bi=phases are amazing. the old roland phasers are great to (not boss). DOD FX20b is good for a cehap phase. the Akai intelliphase is a amazing and CHEAP phase(30 off ebay). I just picked up a old univox microfazer and am really impressed(using it as my second phase now)
Tremolo/vibrato-the dano trem is good and cheap. The Flip tube tremolo is AWESOME. most the rest I really dislike. The MM4 by line 6 has great tremolo and vibratos(true pitchshifting vibrato). The CE-5(slight mod, basically you add a second cable attached to nothing into the output B)/Marshall tremovibe are the only other vibratos on the market. I need to try the marshall again as the jacks are mislabeled.
Distortion - I use a rat. There are PILES of gain boxes and I think I have tried 50% of them. the rat won.
Feel free to add and ask questions. I love answering them.
No one has to be alright all of the time.