My DS has a knitted type blanket - it has holes in it, so is easy for him to breathe through when he throws it over his face.
When he was younger I used to put him to bed and just lay it by the side of him, giving him the corner to play with. Once he fell asleep I would move it out of his way.
I agree with Stacy, make sure you get on that is easily replaceable. My DS will not touch any other blankie as we cannot find the same one. His one is so old and worn and grey from being chewed and washed so much, but he loves it to bits. We darent take it out anywhere with us incase we lose it.