I was tempted to put this in Polls but it'd be a huge poll.
What's your favourite map from the missions?
Mine would be Plymouth 11. Me, I like to mess around on Easy, just for kicks. If you're fast enough, you can choke a few key points with tanks and hold the enemy, and mine to your hearts content. Then the Blight. Pours in from both sides of the map. Left side doesn't move so you think your base is safe, whereas the right-side floods in until all under the lava is gone. Then the entire left side of the map goes purple and spreads like wildfire.