Technically I believe the lightest available switch for this kind of thing is the Cherry MX Red, at 45 cN activation pressure. However, since this is a linear s

Technically I believe the lightest available switch for this kind of thing is the Cherry MX Red, at 45 cN activation pressure. However, since this is a linear switch rather than a tactile one, it's difficult to tell when the switch has activated, and you typically end up bottoming out while typing. The MX Blue switches I use have a the same spring, but the tactile bump gives them a slightly higher activation pressure. However, it also gives you tactile feedback about what point at which you can release, so in practice it may end up feeling lighter. That said, I can put together a kit with Red switches if you like; just put a note in the shipping field. I think the Blues are a better all-around choice (they are still much lighter than the famous IBM Model M's buckling springs) but if you have specific needs I can work with that.