I haven't beaten campagin mode yet but so far I liked "A Leak In The Vegtable Patch" it's fun and you get jetpacks and teleporters. They come in handy as the water rises every turn. I really liked the idea of having the water raised! Another fun mission for me was the haunted level where you had a regular defeat all the other worms. I really enjoy the fighting missions!

So.... what's your favorite missions to play?

i like the mission when you go to hell, and you have to escape from the exploding island

Hmm, this is a hard one. I think my three favorite missions were:
1) Beautiful balloon
2) Earn your crust
and
3) Ragnarok and roll

Dunno if I'm corect but: To boldy go (when u have go up @ ur ship and water is rising kinda fast - didnt manage to pass it). :D
Oh yea almost forgot: and Place Holder that was fun.

Top 5

1. Falling for you
2. Beautiful balloon
3. D-day
4. In space no-one can fear your clean
5. Grim Reaper mission I dont rerember name.

My favourite is A Leek In The Vegetable Patch