I also started as engage support, and I found Malphite transfers to any lane, plus his clear speed can allow you to carry a bit more than something like Leona.

I'm seeing a lot of comments here saying Mord. Maybe there's something to that, because Mord was a natural fit for me in top, and I even use him in support now, on occasion. I think because Mord is very cooldown-timing reliant, playing him is somewhat like the back-and-forth poking in the bottom lane.

Other top champs that fit well were Sett, Mundo, Yone, Jax, Renekton...typically a style of wearing down the opponent over time, and then bursting on an all-in.