Gum *is* my cigarettes, and has been for years; I almost always have a stick or two on me. Like some others in this thread, I only chew sugarless.
The Wrigley's 5 gum flavors listed by Kenickie is pretty good--I just tried the spearmint for the first time, and was impressed by its longevity, though the flavor IMO is not quite as strong as Extra, despite the commercials that make you think you'll have an oralgasm from the first taste. Extra is my personal favorite, though I mix up the flavors enough to keep me from having any real preferred single one. Orbit has some great flavors (like sangria, mmm), but it loses it far too quickly, IMO.