I wouldn't recommend one.

For example, Daniel often pushes his way arount the cot and ends up with his mouth pressed against the sides of the cot. Because I don't have a bumper he can breathe freely. If I had a bumper he would have his face buried in it and that would keep me up nights.

I reckon give your baby as much circulation around them as you can provide. I don't have any toys in his cot either - I like to know he is sleeping completely without any possible dangerous interference.

When he is older (still can't sit up by himself but can commando crawl like a demon!) and can sit up I'll probably give him a teddy then. My worry is getting tangled in decorative things that he doesn't necessarily want anyway.