I really enjoyed the taskforce challenge missions, and you should also try
You should also try them out. http://resource.openra.net/maps/uploader/1087/
They are excellent to make you think differently, and use the resources you have..
It would be sweet if modders could create some more.. Lets make more challenges like this...
Lets let all players try them out, then we can start helping players out, but not with complete walkthrough, but some hints.. After some time..
(Disclamer, I have done all'but challenge! got replays to prove it)