Well, lessee...the Toppobrillo Quantimator does both quantizing and has an onboard shift register. Also, Mark Verbos's Random Sampling combines a lot of Buchla-esque random source capabilities with a shift register. Those would be an idea. Also, there's several quantizing modules that can also output chords based on incoming CVs, with one huge (and very complex) example being the Instruo Sinfonion, and those could be interesting in a generative situation. Using some separate modules might not be a bad idea, either, and would let you pair something quirky like Erica's microtonal quantizer with a couple of Elby analog shift registers for some real strangeness.
Another useful module would be a quantizer; several of these can extract gate/triggers from voltage curves and output a number of different control signals that could then be fed into logic to create even more complex rhythmic behavior. Joranalogue's Dual Window Comparator is especially neat, since it has several different ways of obtaining gates/triggers beyond the usual single crossing-point activation behavior. As for logic, ARC's Artificial Neural Network looks like it has a lot of 'abuse potential' beyond the typical Boolean gates. A couple of stochastic 'skippers' could be fun, too, and Ladik's are pretty cost-effective/
Plus, don't neglect some of the random sequential devices, most notably a Turing Machine. In its full-blown expanded version, it's a generative fun-house! And as for interesting random sourcing, Nonlinearcircuits' 'Sloth' variations offer a lot of slow-motion change across, in theory, several hours. One of those hooked into an LFO cascade as an extra modulation-variance source could get pretty entertaining.
The neat thing about where Eurorack's at at present is that there are SO MANY choices and possibilities, it ultimately makes creating most any sort of device a piece of cake...provided you're willing to wade through the gazillions of possible modules and combinations of modules. But what we have now is raw power on a scale I'd never envisioned when starting off in electronic media way back at the end of the 1970s. Pretty cool!