Basically: whatever's cheap, comfortable, and won't fall apart within a couple of months. I bloody hate shopping for shoes, so I like to make sure it's required as little as possible.
For that reason, I'm a big fan of Converse. They're maybe not the most practical footwear for the winter, what with being canvas and having about as much grip as ice skates, but they're like slippers once you wear them in, and surprisingly indestructible for what is effectively no more than a bit of thin fabric glued to a bit of rubber. My current favourites are some really battered blue high-tops, had them three or four years and they're still going strong. I've got an even older pair of black high-tops but they're not getting much wear since they got covered in grafitti. Got some red ones too, but they're a bit ostentatious for daily wear. The cream ones are just a bit impractical when I walk across a field pretty much every day.
My other regular choice, particularly with all the snow and ice around at the moment, is a pair of black Reebok Classics. Plain and simple, had them four years or so and they're holding together remarkably well.