Orianna for mid, have loved playing her since release and loved playing her throughout every buff and nerf she got...well except her most recent (or 1 buff before) buff that makes her completely easy mode for any new Orianna player now sadly.
Corki for AD carry, he was the first AD carry I picked up and loved when I was still below Lvl 30, though back then he was OP and still had his blind on Q. Unfortunately with all the recent nerfs he's been getting he's not as strong as the other 2 from the holy trinity of AD carries sadly.
Leona for support (role), it's just so fun sticking my ass on the enemy carries' faces perma stunning them and watching them cry as they can't move forever. I also love aggressive play on any lane and absolutely loathe passive play.
Cho'Gath for top, because I can't play most solo tops for shiz and probably because Cho'Gath plays like an AP mid champ (AP carry is my favourite role).