A collection I have been refining for some years... Most all are GUI-Less so they take on the native GUI of the software you are loading them in... Some reject GUI-Less VSTs like Aodix 2.34 & Musagi... There are some in there that have 'minimal GUIs'... Many of these are quite good, most are VST2 but some are VST1 so can be used in old Fruity Loops 1.76-2.71...
https://archive.org/details/611-gui-less-vst-vsti
https://archive.org/details/611-gui-less-vst-vsti