I've seen this used a few times already (well, pre-ambassador re-nerf).

"Man," I thought, "what a stupid pryo..."

*really loud uncloaking sound*

"Oh..."

Rocket to his face.

I like the fact that this actually gives you a good excuse to disguise as a friendly.

I've been working too much to play, but the thought of a full crit ambassador makes me feel all tingly...