Let me preface by saying that I realize there is a Moogerfooger forum. My purpose for posting here is that I have 2 Phatties and I’m more interested in the opinions of users that use the Foogers with their synths/CV, and not at all interested in how a guitarist uses it. So, I’m posting here to weed out the unneeded options of guitar/bass players.
— if you had to choose only 2 Moogerfoogers to use with your Phatty, what would they be?
I would say the 104 delay, the 105 MIDI murf and maybe the CP-251 to be able to add some weird CV routings..
That would be my pick! However the sad case is, I don’t own any of these, so take this with a grain of salt. 
MF104M delay, MF105M MIDI MuRF, MF102 Ring Modulator 
A lot of folks here swear by the MF103 Phaser as well…
I do not own any of theses actually but i will soon get a Phaser from second hand. My first choice if I didn’t have to worry for money will be the Delay ( I use a lot of Delay on Pluck and a lot of very short delay on most of the main sounds, then the midi murf ( which is very cool to add some stereo to a mono synth ).
The best thing to do is to go on youtube and watch the videos about Moogerfooger, there is a lot of videos with synth that are very nice. ( https://www.youtube.com/watch?v=86cD4wmBGWE , without synth only moogerfooger but this serie of video rocks )
At the beginning, I would start with the MF-104 Delay. In combination with a Synth it’s probably the most versatile Fooger. You can fatten up the sound with short delays, or double the sound with a long delay, or do some crazy stuff with modulation delays… the possibilities are endless. On a clean desk, the Delay would be my first Moogerfooger
The delay is great, but requires you to jump into the deep end of the pool. Lot of other good delays out there for a lot less. I would consider a delay a must have, but not necessarily the MF-104.
MF-105M Midi Murf loved mine while I had it. Very versatile! Unique. It does have a distinctive color; so, make sure you like its sound. I dig the action of the envelope control (wish it had a CV out).
I totally agree. The MidiMurf is versatile too. But I think it’s a little more specific in his use. You like it or you don’t. In my opinion it’s not that universal unit as a delay. But you’re right, I love both of too
I would take a look at the Koma Elektronik pedals too.. they have some interesting options too..
I also have two phatties.., and most of the foogers.
After playing around for years trying to find my perfect dual slim/fooger combo, I realised that I like my phatties best raw. I ended up using the 102 and 104z for vocal, and the 107 on my blofeld. (live setup)
102 and 104z is definitely my favorites.
for me all foogers with the m for example 108m for can make really nice sequences when you sync it to your midi clock,
Foogerwise, 104x and 102.
(in 2U module form for me though)
Had the MF-107, sent it back.
I cannot choose between 2, I have to have the MF-102, MF-103 and MF-108.
The thing is, they make my x0xb0x, Virus C and Nord Lead sound awesome as well.
MF 102 103 and CP-251. I swear by these.
for synths, the 104 is absolutely essential . yes there are other BBD delays, but nothing compares to the tone you get from the 104, as well as the delay time and feedback CV control. The combination of the CP-251 and the MP-201 is unbeatable as a multi-mod bus, but also the gas pedal is the most expressive pedal I have ever played. next is the ring mod, and for anything other than moog synths, the 101 filter is crucial.