Mary Sues don't really bother me, honestly.
It's annoying when everyone else has well-developed and meaningful characters, but at the end of the day, it's still someone's creation and it should be respected. Even though it was created out of misguidance and the character itself is completely quintessential.
Sure, I snicker at the worst of them, but I'm never going to tell someone they have a bad character.
That being said, pretty much every supernatural/fantasy/magical roleplay has a character with wolf powers.
Werewolves bore me. Their character traits have become so predictable--fierce, loyal, protective, wild, ect.
Or they act like actual lost puppies with 'insanity' induced by teenage angst and a tragic backstory that would put Twilight to shame.
They go into a blood rage when they see people they love hurt, but gore is boring and repetitive when it's unnecessary. In a good RP, your characters get hurt. It would be a waste of time to kill everything that hurts you--instead lick your wounds and move on.
They wallow in their romantic archetype, the males always independent and stoic and the females are always "mysterious" and transparent.
Wolves are highly social animals--the 'lone wolf' is a misnomer--lone wolves die when they fail to find packs.
Now, what I like to see in characters is strength.
My definition of a strong character usually isn't the same as others'.
Obviously, strength to fight for what they believe in. Strength to carry on when everyone else gives up. Refusal to back down.
But for me, I see strong characters when I see them take initiative. No one likes characters who just hang in the background, waiting for something to happen to them. There's always something for your character to do, to talk with, to find out. I hate being the person to always have to strike up a conversation because every other character is too busy focusing on random NPCs to take note of what's actually going on. I hate that. I hate using random, nameless, faceless characters as filler when I have four or five--maybe more--perfectly good ones at my disposal. But that's a subject for another day.
As I was saying, with confidence comes strength. If I'm in a roleplay, I'm going to interact with everyone and the environment as much as I can.
But, yeah, I hate using filler people and I hate tragic backstories if they're not executed well.