Best Free Midi VSTi plugins

[WarpCanada]

Awesome here are some more for your list:

SURGE: Free, Open/Source
https://surge-synthesizer.github.io/

PENDULATE:  Very weird, awesome free synth. From Eventide who doesn't make anything that isn't awesome.
https://www.eventideaudio.com/products/third-party-plug-ins/chaotic-generator/pendulate

VITAL:  The best free synth there is. If you can afford to slide the author some coins, do so, but there's a free version and it's full featured.
https://vital.audio/

[chapperz66]

I really highly recommend the free Labs instruments from Spitfire Audio.  There are loads of them and they are free and very decent.

[TPB]

I would second the spit fire I downloaded the free ones last month and have been really impressed with the sounds
Tim

[maxit]

This is a yamaha C7 piano, quite standard, but if find it's the best sounding one amongst free pianos. Sometimes I try something else but it ends going always back to this one.
https://neovst.com/piano-one/

[ianjm]

I use synth1
Downloaded a s&%t load of presets for it (16000)
Just going through them and put the good ones in a bank

[64Guitars]

Awesome here are some more for your list:

SURGE: Free, Open/Source
https://surge-synthesizer.github.io/

Surge XT version 1.0.0 released January 18, 2022 for Linux, macOS, and Windows.

I've added it to our Free Soft Synths page.

[WarpCanada]

Another for the free list:

Decent Sampler (plugin, sample playback)

Songbook (a website with thousands of free sample packs and playable sample based instruments, for Kontakt and DecentSampler, and SFORZANDO formats, as well as just plain .WAV file based sample sets)