TAL modular , not free but cheap and stunning sounding ..especially now ..since it's stil in beta release .
Cheap and awesome ..toneboosters stuff ...track essentials = 25 euro , ferox is pretty awesome and is included in the bundle
KLanghelm ..amazing and cheap as chips .
Best freeware synth ..( according to me that is )
daichi synth 1 ( old ie but goodie..based on nord lead 2 )
dexed ( dx 7 clone )
charlatan ( basic synth with great zdf filters )
sq8l ( oldie but goodie , sq80 emulation )
Pg8x ( roand jx8p emu )