RA_apathbeyond is also a favorite of mine. It would almost need to be remade from scratch, as the version that we know is much too large. That being said, it probably wouldn't have to be shrunk too much because we have sprinting now.
No comment about the ants
Someone mentioned alpine lake earlier. That was also a really good one IMO, even though it had some issues. I think it could be fixed though with some love. It had lots and lots of infantry tunnels! Also, I'm going to be that guy and bring up RA_FinalBarricade! I liked that map a lot, even with all its flaws.