Animals:
Real: A burmese cat, could control humans through lovability
Fictional: As unit leaders, The Graboids from the 'Tremors' movies, along with Shrieker drones. Their underlings could be the Assblasters (Tremors fricken ruled! Go Burt Gummer!)

Plants: Was going to say Venus Flytrap but Megs already bagged that one, so I'll say a huge Gum Tree just because I'm a lad from the bush and I love the idea of them coming alive ent-style and stomping the hell out of one of those arsonists!

Non-Vehicle Machine: A toilet. Just because I cant think of a time that humans are more vulnerable and, appropriately, a Decepticon Toilet would scare the s#%t out of me! And man, would that bot have a grudge against humanity after a while!