I'm good in making it sound natural. (Relative to the context tone or emotion)
Spelling. A bit unimpressive with today's easy access to the dictionary and spell check features or softwares, but I AM good at it though. :)
Catching repetitiveness, awkwardness and boring flags. I'm gonna be honest, I'm also prone to these mistakes that's why I always take my time reading my own works again and again, revising them as much as needed before publishing.
I'm also a bit good in catching OC parts (Out of Character parts), and like I said, I'm also prone to this mistake so I do take my time making sure everyone's in character.
I've got an eye for flow and continuity. From the textual sense to emotional sense of the story, I like making sure that everything flows well and realistic.
Romance. I have written romance since I started writing. It's something I love reading and writing. I am born for this shit, (not a prodigy but you know, I just love its idea so much.) I am particularly good with fusing romance into everything. Comedy, angst, friendship, hurt/comfort...(You name it, I romanticize it!)
Angst. I've written quite a few for angst (Nowhere near pro but I've become better at it and willing to help out).
Note: I might suck at my own works sometimes but I can easily detect areas of improvement with works of others.