A few pieces of light rafting gear I’ve tracked down…
Baltic Aqua PFD 12.5oz/355g. http://www.baltic.se/product.asp?prod_id=45&lang=eng. Note that I believe this has less flotation than equivalent US PFDs (eg MTI Livery), because the European safety standards are different (50N is the European standard, whereas US Type III is 15.5lbf which is 69N). Not particularly straightforward to mount a knife on though.
Cold Steel 2" Super Edge 0.8oz/22g. http://www.coldsteel.com/superedge.html. Simple, light serrated fixed blade knife with a point - there are several river knives with a blunt tip, but I wanted one with a point so I could easily puncture the raft if needed. The sheath has a tight enough grip that I don’t worry about it coming out, yet it’s simple and fast to get out (no unfolding) and makes for easy mounting.
Granite Gear Uber Light CTF3 Dry Sack (cuben fiber). My 18L is 0.74oz/21g (!). These are new in the last few months, and aren’t listed on the GG site that I can see, but I got mine from http://www.prolitegear.com/granite-gear-uberlight-ctf3-drysack.html. Lighter and more waterproof than silnylon sacks - the seams are glued/taped rather than sewn, and the fabric is a film rather than woven like silnylon so it can’t wet out or leak under pressure. I’ve never had a cuben sack leak; I’ve had plenty of stuff get wet in silnylon sacks (admittedly silnylon does vary in waterproofness). Good rectangular-ish shape. Expensive though.