I'm posting this under the assumption that we're talking about lightweight, unpadded shoes in general. If I'm wrong, sorry.
The lightest shoe I've seen (and that I'm looking to buy) is the Vivobarefoot Ultra. A pair of EUR 43/US 9 (Men) is 190 grams without the insole or tongue, compared to VFF's 301 grams. Might not seem like much, but I'm looking into buying these for two reasons: One being that I want the lightest shoe possible as I travel with carry-on luggage only and need to keep the weight down. Reason number two is that my toes are quite long and not a perfect fit for the Fivefingers.
The one problem I'm anticipating is that they're said to be a bit on the small side, and that you might want to buy one size up from what you normally would. Thing is I'm a EUR 47/US 13 and that's the biggest size I can get my hands on. Ideally I'd get a 48. Then again I think the +1 size recommendation is made with the insole and tongue in mind, and I won't be using them anyway, which'll buy me a bit of room, I'm sure.
Anyway, just thought I'd toss another alternative into the mix.