helmet - try as many as possible as different models from the same manu8facturer can fit differently. look for ease of adjustment so you can add a hat under the helmet in cold weather
reflective jacket/vest - for colder weather a jacket with good ventilastion, no elastic on cuffs. Front closure by poppers and zip so you can let more air through as you warm up. For slightly warmer weather I have a Karrimor sleeveless vest. In summer I dont have anything over the jersey.
repair equipment - Topeak multi-tool + tire levers as these are the tools you will need most and are a lot easier to use than the ones that come on the multitool. Spare tube + patch kit as it is possible to get multiple flats in a day.
pump - I have been happy with my Topeak Roadmorph. I think the similar one by Lezyne is a bit bettter, but I hadnt seen it when I bought my pump.
lights - the Planet Bike Blaze 2W LED is fantastic ($35). I also use at the front a white blinky, an 8 yr old Cateye EL300 and 2 $store LED flashlights. 2 red blinkies at the back.
Carrying things on bike - I only have a light-weight cable lock on the bike, and leave the heavy U-lock on the rack at work. I keep shoes, towel, shampoo, slacks at work. I carry my lunch, shirt underwear and tools in a trunk bag on top of the rack. If you go for panniers get a rack with dog-legged stays which will stop the rear of the panniers swinging into the spokes if you make a sudden swerve.
Other accessories - fenders. Waterbottles - I have Camelback Podium bottle but they are not really worth the cost. Look for soft bottles that are easy to squeeze and have a spout that allows a good flow of water. Gloves will prevent pain on hands when you fall. Take-a-look glasses mount rear view mirror - this is particularly useful if you have to make a left turn across multiple lanes.
Cyclocross with triple front der - drop bars are a godsend in headwinds. 28 mm tires (foldable) are light and fast, but will tolerate unpaved paths, shortcuts across undeveloped land and parks, and careful curb-hopping.