Here's mine to start.
Showdown- Closed gates limit traveling
Pipeline- I like it for S&D games but not TDM.
Station- Too many corners
Wasteland: No cover, hard to get people out of the bunker, the radioactive zones are annoying, and if somebody calls in air support, you gonna get R4PED!!
Scrapyard- small size makes it hard to call in care packages without somebody finding you and stealing your loot.