For a majority of my characters, I have no problem getting into character:
Daniel - Nice guy all around, a bit high strung, sometimes a bit too preachy about morality, devoted friend and family man.
Stephan - Is of the mind that much of the world is full of corruption, especially the people in it. Distrustful and rude to strangers, but can be kind and considerate to people and causes he cares about
Midoku - Shy and softspoken, yet exceptionally curious. Friendly to those he knows well, though his significant other often brings out his less-than-cheerful nature when it's necessary.
And the list goes on. However, there's a character I have nearly as old as this trio, who I've never been able to settle a set personality type on.
Jonas Kilmett - Werewolf husband and father.
Sometimes, I've played him as a softspoken, hardworking family man. Other times, as a loud, "man's man" type. Other times, as an angsty, self pitying whiner. Much as I've tried, he's my one character that I can't seem to "Get into" properly. When the time comes when he's needed, I find myself fumbling for things to have him do. Maybe someday, I'll finally get the inspiration I need to cement it down, but it's been a trying process over the years.
So, that's my own story of a troublesome character. How about the rest of you? Any characters who give you trouble, or still lurking in the character closet awaiting finishing touches?