Rumble, Vlad, Trundle, or Riven

Add Swain to this.

Riven.

Good early, has a shield, jumps like a rabbit here and there, her runes are easy to obtain, has a nice pool of skins to choose from, high elo competitiveness, can carry games if fed. jungle - viable.

Trundle.

I got him, he's a troll, he's cool & funny, good early & sustain on lane, you can misplace an E and make you teammates die, awesome ultimate, easy runes, you can build him tanky with damage, you may not be able to carry games with him. Jungle - Amazing ganks with E.

Vladimir.

I don't play him, needs some time to master if i recall right.

Rumble.

i don't play him. Super galaxy combat breaker!

Vlad main here, he is a lot of fun if you can pull him off, but can be challenging at first, I would suggest him if only because I main him :P

Early game midlane he can easily harass his opponent out of farm with his q, until he is able to land stable kills with his ult+ignite combo. If you do grab him my #1 tip is to not grav spell vamp items like will of the ancients, as there are better things to grab like twin shadows, or spirit visage.