Several years ago, Sarah and I were at a loss for what to do for my dad for a gift at Christmas. I'm not big on buying stuff for people, but I already had built him a bike (and anything else made of metal I could think of) so we had to get creative. The Pojaque river runs behind his house in New Mexico, and it's really hard to find a place to cross to get back into the Barrancas (fingery dirt mesas) on the other side, which is a bummer because it's a great place to go run, or walk the dogs.
In any case, the conundrum resulted in this mighty bridge. It's a 2x4 with a chain holding it bowed, and a rope so that you can drop it to the other side under some semblance of control. It works great, and I think it's the best Christmas present we've ever given.
I would have posted it sooner, but the pic was on my sister's camera (that's her on the bridge) and she didn't get around to sending it until today.
Custom bridges start at $25, plus I get to raid your fridge just like at my dad's place.