Speaking of great dialogue, The Unit is another one that's very underrated, barely anyone I know has seen or heard of it. It's got some of the best dialogue of any TV show I've seen, really has an authentic feel to it. The wives' storylines get a bit annoying at times but it's easily forgiven.
Yup The Unit was excellent, easily my favourite proper military Tv show (Band of Brothers doesn't count as it was a mini-series). Excellent action and dialogue, just a shame high production costs mean't we didn't see a final season before it was wrapped up.