Taking the question literally (having to spend the money in a year) that seems one of the best things one can do (one could even argue that is not spending, if half those getting the money put it in the bank), as it could lift many out of poverty.

Give me a decade and, maybe, some really useful projects might surface. Ten years of time and a trillion dollars might be enough to go to or maybe even start a colony on Mars, for instance (http://en.m.wikipedia.org/wiki/Human_mission_to_Mars#Challen...), or to get rid of malaria.