Starcraft's Zerg were an intresting lot (as mentioned before).
Many had recognisable features, like 2 eyes and a mouth, but you only really saw them in the unit 'face box' down the bottom. On screen, and in battle they were really just purple pulsating blobs.
The queen was probably the most unique, it didnt have anything that could have been inspired by anything known to man. Where as hydralisks were sort of like a snake V porcupine creature, and even the mutalisk had flapping wings and a lizard tounge... the queen was just ****ed up.

Ps, its a flying unit, if thats not apparent.