Favorite- Triangle ... when I have a tight triangle locked in i feel like a total bad ass.
Best- Guillotine... yea its the easiest submission but once i have it locked in whether its standing, in half guard, or full guard I have yet have anyone my size escape.
Worst- gogoplata... I need to work on my flexibility. Even Triangles are hard for me but at least i pull them off. Never successfully pulled off a gogoplata... sad.