Arh, such a hard question OP. Id guess taking care of a larger pet is something that is very annoying, thankfully I never had to do that.
Id go with laundry, or washing dishes Id guess. Not really sure witch is worser.
Edit: People often vote bathroom, but lately Ive had my own bathroom inn the house, its so much easiere to keep it clean then When I shared it with my brother it was quit harder, he always made such a mess compared to me. So yea, if you only have you're self to clean up after its fine, takes like 20 minutes tops for me to really clean it well.