I personally like Death Knights, Phoenixes, and Water Elementals (because they have powerful magic).

Added 7 minutes later
By the way, I saw a mod on one site that allows you to turn zombies from the Necropolis faction into mummies, but this mod only works for the Tribes of the East. Also, mummies can be upgraded in two ways.

Added 31 minutes later
In general, if anyone is interested in the mod that replaces zombies with mummies, check out the screenshot. http://hmmp.ru/_ld/1/01685.jpg

Added 4 minutes later
By the way, that site where I downloaded the mod has many other mods. Here's the link: http://www.hmmp.ru/news/2