Best pet to have? (GA lvl 5+) (Ended)

Yesterday i won a Ryse: Son of Rome GA, and today a friend of mine gifted me some Monthly Bundle keys!
One of those, surprisingly, was Ryse: Son of Rome, which i want to give to this great community.

IMPORTANT - HB says it cant be activated in RU/CIS

In order to enter GA (lvl 5+) you have to solve this ridiculously hard puzzle

Please, tell me your opinion on best pets to have :)
If you know good steam backgrounds and badges with rats, share your knowledge!