Zest is so damn solid. He never seems to mess up and more often than not he wins games from disadvantages. His only weakness seems to be his preference for unnecessarily wacky builds in bo1 games, which has cost him some rank in Proleague. He has ridiculous winrates in bo3+ though. (eg a 100% win rate in bo5+ this year)
When Maru is on fire, and he usually is, he can beat anybody through raw micro. At the same time, his macro and gamesense are superb. What he's lacking the most is easy foreign tournaments to pwn noobs in, I think.
soO is really scary. He seems to be a bit nonchalant as well, almost to the point of throwing games against weaker players (watch his GSL group) just because he doesn't care. Similar to Soulkey, he plays almost every style in the book flawlessly. Reaching two GSL finals in a row, and then reaching the GSL GC ro4, he is really consistent. But not yet winning.
Rain is very consistent. He has been in the middle of every power rank since 2012, I think, and with good reason. He also suffers from the "not winning anything" syndrome, atleast until he won the Hot6 cup in the end of last year.
Coming in as a GSL champion and soon to be Nestea award winner, Soulkey is very similar to Rain, except that he placed second in the Hot6 cup.
Very strong player. His only weakness seems to be stress and emotion during tense situations. Plays really well most of the time.
Somehow Parting has managed to never look stellar but beat almost anybody anyhow, and with the recent Nestea award it would be a bit rude to not include him in this list.
Once a blazing royal roader and now just a good player, Life seems to be on his way back to form. Let's hope he does, at least.
He knows how to macro better than anybody. Recent foreign adventures (ATC, DH etc) has taught him about how to hold cheese. And now he is back in Code S to pwn everybody. I hope.
byul - Has looked like a future superstar several times in PL but then falling back to being merely okay
jjakji - He is playing better than ever and showing he was no one hit wonder when he won his GSL.
mma - Slowly climbing his way back to the top and invoking nostalgic fanboy feelings, similarly to DRG, jjakji and Innovation.
sos - Famously 'casual', he is a very good player, but only seems to win things when he feels like it. (id est when there are 100k USD prizes to be had)
rogue - Showing moments of sheer talent and brilliance but never performing. Perhaps it's the Artosis curse?
DRG - He is back and better than ever, but the same is true for the scene in general so he isn't a top contender yet.
bbyong - Yet another player with huge potential that hasn't really had his big breakthrough
roro - Consistent and ever evolving, but always a bit under the radar.
dark - He could be the next big zerg, if his SKT teammates Soulkey and soO don't take all the glory for themselves.
hyun - Still clinging on and playing a lot of tournaments and having a fair amount of gosu moments while also losing to the top players on a regular basis.
Honorable 'oldskoolers doing well' mentions:
jaedong, mc, bomber, mvp, stork, flash