The Zomboni.

Zomboni is a zombie, well 'Space Ogre' anyway, that drives onto the lawn in an ice machine, which leaves an ice trail as well as crushing your plants and being very tough. Nothing can be planted on the ice, but it will melt after a while.

Health: High

Strengths: Very tough, leaving an ice trail, crushing plants

Weaknesses: Instant kill plants, Spikeweed/Spikerock