I watch the Shield sometimes; you really get hooked when you start watching an episode. I wish I watched it from the beginning though.
Other show I never miss are Smallville, Dark Angel (when it was on) Gilmore Girls, Alias, Will & Grace, Charmed (I'm not really into it as much as I used to be), Big Brother (when a new season starts), Dawson's Creek, Firefly (was good while it lasted), Less Than Perfect, Everwood, & Good Morning Miami, Roswell (when it was on), Miracles, Veritas: The Quest, Birds of Prey (watch it all, but thought it was kinda stupid. WB started good with Smallville, and now they ain't stopping...)
Shows I occasionally miss and don't mind are Fastlane, Boston Public, Survivor, & Conan O'Brien (not really a "show", but I love him lol)