Thanks for all the replies thus far.

weavers and bikinpolitico: I did briefly consider a cyclocross bike, but I think I will end up with both a MTB and a fixed gear bike at some point in time, so I don't really need a bike that does both. I'm just wondering which would suit me as a rain commuter best. Whichever I choose will be bought first, the other will have to wait until I save enough spending money from my budget to purchase another bike.

BarracksSi: I'm actually open to either a fixed gear or a single speed. Thanks for the input, I hadn't considered that configuration.

Yan: Definitely - the ease of maintenance is the only thing that is starting to sway me toward the fixie/ss route. Reliability will be key in the inclimate weather.