Definitely multithreading using threadpool in data intense apps, given up so many times trying to use it now .
I love the .NET ThreadPool soooooooo much. It's basically my goto for running anything in a multi-threadeed environment that I can just set going and not worry about until its done. What language are you using?
My biggest weakness would be starting a new project with no idea how to implement it. I just jump in do as much as I can around the idea (splash screens, menus,...) then try to learn the best way to do the main idea. Realize that everything has to be changed...and start all over..
So much to learn and so little time.
Biggest weakness I have is a complete lack of free time to work on the projects I have in mind. Things have been far too hectic around here lately with my wife just having her gallbladder taken out a week ago.