What Am I Again?

Apparently I am a snake

Deceitful and cheating.

But then I'm a mosquito

Meant to be swatted.

A rat

Ugly and complaining.

Or maybe a swan or puppy

Sometimes graceful, sometimes hyper.

So what am I again?

I can't be all of them.

Or can I?

Sorry my adjectives aren't perfect or fitting. I'm not going to come up with an excuse for that.