This seatpost weighs only 165g when cut down to 240mm, saving up to 128g over a generic 300mm seatpost. In the original form at 385mm, it weighed 221g. It resembles a Thomson seatpost, but lacks features like the angle adjustment markings. However, like the original, it features an oval bore, an integrated head, spherical washers, and a wide clamp area. Unlike the Thomson, the bolts screw into aluminum barrels, saving an extra 5g compared to the steel ones Thomson uses. These should be plenty strong however, because many other two bolt designs screw directly into aluminum seat clamps. Compared to a Thomson 27.2 x 240mm Masterpiece, it weights only 7g more and is considerably lighter than an Elite. For each centimeter removed, the weight will be reduced a little over 4.1g, but remember to leave enough post for safe usage. It should be noted that these do have a 80kg weight limit. In stock form, at $15 and saving 4.8g per dollar, it represents an excellent value, moderate cost upgrade. This increases to an exceptional 8.5g per dollar when cut down. It can be found on eBay.
Price: $15 [Moderate Cost]
Value: 8.5g/$ ($0.12/g) [Exceptional Value]
Recommended with caveats
These seatposts have a 80kg weight limit, and are zero setback, so they are not for everyone. However, they are light, and there is little to lose by cutting them down for further weight savings.
Also see GUB SI Seatpost which is both lighter and cheaper, but may not work for everyone.