I don't see how anyone can go wrong with an M14 with a Masterkey Shotgun for Hardcore TDM. It's a solid gun with strong mid-range power and frightening accuracy if you can let the sights settle. That shotgun has saved my sorry hide several times. Paired with a CZ75 Full-Auto and you have a package.
For all those favoring full-auto assault rifles, how can you possibly go wrong with a Commando w/ Red-Dot Sight or a Galil with an ACOG Scope? Both have advantages over the other and that's why it depends on the map which of those three I use. But when you want to lay down someone six feet under with extreme rate of fire... what's wrong with a Stoner 63 with a Reflex Sight?