There's been a long history of "overpowered" champions staying just under the limelight in solo queue, but then suddenly rising to popularity once they change to a different role, even if that's not their optimal location.
The idea that "wow...xxx is SO overpowered that they can even stop lane as a xxx" is hard to get out of our minds.
Examples
Taric support - 60% win rate shifts to top and jungleWukong (mostly top) - 55% win rate shifts to jungle
Nunu - Pre-reworks, shifts to Top
Vel'koz/Brand - 53% win rate shifts to support
Braum (on release) - Played as top and jungle, now stuck as support
Maokai - Shifts to Top
Rammus + Sona
Currently Rammus and Sona both have respectively, top 3 win rates in solo queue and have held this position for quite some time now, Rammus especially.Rammus
Rammus Top provides insane damage mitigation and catching power, while also providing strong jungle gank support combined with strong split pushing damage. All in all, his biggest weakness is against ranged mages, but even if he can get close enough for a taunt he can outtrade the majority of them (except Swain),
While by no means a first pick priority in this world of heavy ap tops (eg Ryze), the fact that he's normally a jungler gives him the ability to swap out if the lane match-up isn't in his favor. Additionally, even though his early game isn't very good, his come-from-behind power is immense. Getting tower dove is no problem with him with his innate tankiness and taunt, and he can always powerball out of a sticky situation.
This Plat Rammus had a rough start vs Irelia, but once he got the ball rolling...
Sona
Sona currently has an absolutely insane heal + damage + utility balance as a support, and can easily snowball a lane by herself. While she still has trouble early game vs heavy burst type champions, if she can get to 40% cdr and enough mana regen, she can take out 1/3 of a squishy's health while simultaneously healing for 1/3 at the same time every few seconds.
As a mid laner, she gets many of these perks with the added benefit that she can harass early game against many people who as mid lane mains, don't really get the experience laning against her, and thus don't know her effective range.
After getting chalice and Lichbane, she can easily annihilate single targets with her powerchord. She's also very versatile, and can build a morellonomicon if you have a jungle that's blue dependent or is trolling (welcome to solo queue).
The only drawback of placing her mid rather than support is that as a mid laner she's forced to CS, whereas as support she can hold onto her powerchord for longer.
This Plat Sona fought a Fizz and lived to tell the tale
Conclusions
There are a few champions out there that perform best in a certain role. However, if they're strong enough, other roles are definitely still possible simply because of their insane base stats and utility scaling.
Got any more of your favorites? Think these two have a shot at the big leagues? Comment below!