Which of these champions should I buy...

I saved up IP and now I can't decide which champ I will buy. I play mid and jungle primarily, but I also go top sometimes. Here are my options:

Top: Yorick (Friends enjoy playing him) Riven (Enjoyed playing her while she was free) Jungle: Trundle (Really fun champ) Skarner (Again, really fun champ, and I'm pretty good with him) Sejuani (Friends say she's good and she looks fun) Mid: Kog'Maw (Really fun when I played him AP) Ezreal (Again, fun when AP)

Which do you guys think are the strongest and most fun to play?