Yeah Reavers are just crazy people.... really crazy but still...
I also agree the the infected from 28 days later at not zombies...
The dead thing is a requirment of zombie... though in some cases the change happens at the moment of death so there is no visible dead period.
But if you consider some of the infection types shown in Res Evil.... when some one was infected with the T-Virus but didn't die before it mutated that changed into something else (Alice super human Or Matt becoming Nemesis) Everyone that died before it mutated within them was just a zombie.
But yeah if something looks and or act like a zombie but never did it is a "zombie-esque"