Here is a very good mod that takes the gruff military characters from Call of Duty: Black Ops 3 and replaces them with the cast of the Neptunia JRPG series. Even in the singleplayer campaign, even in zombies mode.
Specifically, in case you were a fan and were wondering, the models have been borrowed from the PC version of 2017's Cyberdimension Neptunia: 4 Goddesses Online.
It's just a visual swap - as in, there aren't new voice lines to go with them - but that only makes the whole thing better.
The mod is the work of a six-person team made up of Compile Heart, Idea Factory, Tamsoft, Kuroyasviel, RandomTBush and Loyalists.
Here's what it looks like with zombies:
You can get it here.