I tried Singed and it was awful the first game. The other team had no real tank, Renekton was closest. We had Garen, Morde, and myself as Singed, Akali, and Nidalee. I kept telling everyone stay together and push. Of course they didn't. Garen blamed me for us sucking (we had taken down 1 turret which I had done by myself). I could never do anything b/c no one was with me for me to flip one of them into my team. Eventually Morde and Nidalee gave up, Nidalee spelt "$$$" in wards.
Another game I was Nunu and took charge of the team. We had the advantage since they were all squishy: Fiddle, Annie, Teemo, Veigar, and Tristana. We had Nunu (me), Malph, TF, Yi, and...I forget, Poppy maybe?
Anyway, Yi insta-locked to jungle. Then when the game started, he said "Sorry guys I don't speak Enlish well and don't know how to jungle." I hoped he was kidding but he clearly didnt since he could barely get blue buff on his own. I took control at that point and told him to lane with me and it worked out better. We won because they couldn't win team fights after a certain point.