Plaits: My favorite, it's a macro-oscillator, very easy to use and modulation, also has beautiful voices. Must have it!
Galilean Moons: It's a brilliant module. You can use it as VCO, Envelope, or just some small fx. It's originally an expender from another module, but you can also use without that (i always use it alone).
Chord v2: A polyphonic oscillator, making chord of course haha but beautiful voices. Normally the one module can only make one voice, if you wanna make a chord, you'll need...............
Prism: A multi signal processor, it has 2 stereo input and 2 stereo output, the best thing is, besides the normal control parameter, it has a "filter type" control with CV, also can use in clock input. It has lots of fun function, can add more changes to your music.
Filter 8: It's a multimode filter and 8 phase oscillator. You can see so much CV jack on it, so just patch it and twist it, you will get lots of surprises, trust me~
ABC: Very useful mixer, because of it so tiny, just 5HP, and have 6 channel. Super for the small set.
Audio Interface II: You can use it to connect your external line level instrument, fx units, synths or drum machines that you can play along with your eurorack. You can also patch it out to a DAW or whatever you want.
Disting mk4: Very very very very useful module in just 4HP. It has hundreds function inside, whatever what features your rack missing, it all can give you. It also has a micro SD card slot, support audio files, it can read loop marker in audio files, MIDI files, MIDI/CV conversion, scales files, and playlist files for all forms. Just need to read and find the function code you need in the user manual (too much to remember!)
Erbe-Verb: A DSP Reverb with many control options. ( if you have some external reverb device like guitar pedal or any hardware, you can also use those, the difference is those are not eurorack, so it's up to you. My point is, if you want to put something more interested modules in your rack, but out of the space, than you could consider that option. Or you could buy a big case at first then put them all inside hahaha!)
Maths: A analog computer, based on tradition Buchla's Algebraic Processor. Legend!
Belgrad: 1976 Dual Peak Multimode State Variable Filter. Like the big knob design.
FLXS1: 4 channel 64 step sequencer. A great sequencer with multi-function and colorful design. The only thing is, just 4 channel, not enough for a big set, but super for the small set. Or can also work with different multi sequencers in the future, they are all can sync with the same clock.
Spherical Wavetable Navigator: Six channel synthesizer with six wavetable oscillators. The chords and modulation are great, just a little hard to trig the right chords in sequencing, but lots of possibilities. Im still working on it.
Shapeshifter: Dual Complex Wavetable VCO, multi voices choice, a lot of modulation and control possibilities. It has preset sequencing and morphing, delay based resonator, 64-band vocoder mode, analog wavefolder, detuneable 8-note chords, extensive sync, pulse and mod B options etc. Very useful module.
Pressure Points: Touch Controller / Manual Sequencer. It has touch plates, if you wanna play something by hand in your rack, you can use this. (you can also use the controller / keyboard who has cv output to play with your rack.)
Loquelic Iteritas: Super powerful voice, it's really awesome... If you like the characteristically wicked voice, that's it. BEST one! When i first time patches it and heard that voice, it shocked me out, i really got physically attacked by its voice. I think you can use that voice, this module, to kill someone, no kidding... I can't use it more than 5 min, it quite hard to stand, so still not succeeded in making a single patch with it... Just take a listen, you will see...
Eloquencer: Best Eurorack sequencer, i think everyone has it haha. Just a little bit big for a small set.
Rene Mk2: 3D cartesian music sequencer. It's a unique sequencer, different than others. If you have space, could have some fun with it.