Here is list from the top of my head.
Ratso (duh!)
Rattigan
Ratnor
McRat
Ratty
Rollsrat
Ratine
Isaac
Ratrine
Rattlerat
Comestible
Jake
Ruby
Red Rat
Ratrum
Battle Rat
Boon
Gullyrat
Cat Rat
Bully
Brimstone
Louise
Sinner
Robby
Royal with Cheese
Vinny
Victoriat
X-Rat II.
Widdle Zergling
Anti Rat
Gordon Freerat
Millie
The One
Snuggles
Neon
Prinny
Ratticus
Smerve
Chinchin
Big Bob
Ratmail
Outratter
Toblerone
JabJab
Smirk
Answer
Kojak
Beth
Leroy
Floggy
Boo
Dreamcatcher
Loko
Queef
Stinker
Breeder
Sock
Gretchen
Expectorant
Iron Ration
Slice of Life
Anti-Dog
Peta
Earthling
Sniffer
Wormtail
Mahogany
Skaven
Tickling Killer
Pointy-Head
Scarf
Third
Zed
Loveless
Nimrod
Katyusha
Ratlass
Nimble
Clubby
Shocker
Smöre
Lemmy
Dickens
Top Rat
Need
Calliope
Fangy McFacebite
Zoom
G-Rat
Utterly
Zoinks
Watts
A+
Lax
Melon Breath
Pinch
Last Resort
Squeeky
Yolo
Namu
Myoho
Renge
Kyo
Alibaba
Slash
Vest
Phelan
Odin
Seppel
Gnatz
Wedding Crasher
Sugar Cube
Destroyer of Worlds
Mephistopheles
Faust
Bepis
Witty
Zanderflex
Forced Labor
Reason
Leif
Spengbrapp
Putty
The Line
Kazabubu