Would've gotten a singlespeed 20+ years ago when I started commuting in Chicago. A hardtail mtb w/1.75 SMPs and Mr. Tuffy tire liners. Did SMPs even EXIST back then? Would've learned to build my own wheels THEN instead of 17 years later.
Rack and trunkbag instead of a backpack. Tire levers instead of 2 screwdivers.
NR Trailrat(old school...2.2 lbs) instead of the virtually worthless Cateye I insisted on using because it was cheap. Would've hung on to the old flowered shower cap I used as my first helmet cover...it got thrown out in a foolish fit of embarassment. Would STILL be using the old White/w/orange stripes Bell helmet I found at a thriftstore for .99. It rocked and was almost bulletproof. I'd have told a bike snobby salesman at an lbs to go eff himself for his condescending tone he took to my newbie questions early on. Better pump...but the old Zefal I had did the job when it was needed. Can't think of anything else, though I'm sure there's more...Oh, yeah I'd have learned how to tango.