As others mentioned, Form is amazing. Itās one of the most rewarding sample-based vst tools Iāve used.
Prism is really good, think of it as a polyphonic MI Elements.
In the factory library I like Gaugear, Junatik, and Grainstates/Travelizer.
For free instruments, GRIP is a must-have granular tool, a modern classic.
Basically everything on the boscomac page, but highlights include Air Piano (ambient piano), Snowflake (generative pretty sounds), Artefact (glitchy madness), and Floodverb (beautiful verb with infinite mode). Iāve kicked money their way in the past because Iāve used so many of these tools.
Other excellent community synths include the 8-voice Sirius-8 and the Buchla inspired West//.