Depending on the weather, I wear a fleece vest (get one with arm holes that fit closely to your arm) a repro A2 flight jacket, or a "field jacket" type coat. All provide good coverage, although the vest has to be at least partially zipped for true concealment.
On of the best multipurpose jackets for a variety of non-Absolute Zero temps is a good, old fashioned denim jacket. The thick material helps hide printing, partial fading helps to blend shadows that might form from printing, plus they are durable and recently have come back into style, although who knows if they will last. They are good to war from 40 degrees to 65, cooler if you have a thermal shirt on. Here in Texas, I can wear one during much of the winter. If I need to wear my ski gloves, then I don't wear my denim jacket.
If you mean jacket as in sport coat, I would recommend an heavily patterned or textured jacket, like tweed. I would stay away from overly thin materials, and if I were looking at a thin one, I would tend towards darker colours or aggressive patterns. Corduroy is a decent choice for either a sport coat (don't laugh, they can look fine depending) or a casual light or heavy jacket.
[This message has been edited by telackey (edited 09-26-2001).]