I commute on a Specialized Hard Rock from 1994, with rack and fenders and slicks. It has front shocks which I like. It's a really bombproof bike for city-riding, and I see a lot of others around and they have a good reputation for being indestructible. So if you're going used, look for early/mid 90s Specialized bikes - they were still steel then.

For new bikes, I've been recommending the Specialized Sirrus a lotfor urban commuting. It's light in case you have to bring it upstairs!

I have a cross bike which I've considered commuting on, but I'm too lazy to add fenders to it SDER