Basically any weapon that had its job done better, and the gun that was better than it was available earlier.
Currently, all I can think of is the .357 Magnum in No More Room in Hell, a recently released Source mod. Less shots, slow firing speed, slower reload, less accurate, uses more rare .357 rounds, and I don't think you can use the Maglite in conjunction with it. The Colt 1911 is better in most ways, since with both, so long as you land a headshot (which is easy with zombies) you get an instakill.
Currently, all I can think of is the .357 Magnum in No More Room in Hell, a recently released Source mod. Less shots, slow firing speed, slower reload, less accurate, uses more rare .357 rounds, and I don't think you can use the Maglite in conjunction with it. The Colt 1911 is better in most ways, since with both, so long as you land a headshot (which is easy with zombies) you get an instakill.