+1
Leafs are completely silent, but not available for your modern joysticks.
But, I recently got some Zippy switches that are significantly softer and lighter than cherry switches. Under the CP they are virtually silent. I believe all the usually suspects (vendors) carry them, groovygamegear (though re-branded with Groovy, they look very similar to Zippy's), and Paradise Arcade.
I put them in a couple Seimitsu's and they have a very awesome feel. With a sub-20gram actuation force, my joysticks have a little less actuation resistance, accompanied with a round gate they make for a great shooter/shmup experience.
Next I'm going to put them in some JLF's and see how they feel for Versus Fighting games.