It's gotta be my favorite. At first ,I wasn't interested at all. I watched the anime dubbed on Toonami and was like "really? he can stretch? lame...." but I made a huge mistake. One piece is amazing! I gave it another shot, subbed this time and I've been hooked ever since. I like it so much that I'm always on the lookout for theories or anything related to it.
When people tell me that it has too many episodes I'm like....
YOU HAVE NO IDEA WHAT YOU'RE MISSING!!! This is an epic tale that grabs ahold of you and never let's go. As you begin your journey along side Luffy, you start to believe in him and his dream. Then your family starts to grow as more characters are introduced. Soon it's just you and The Strawhats off on adventure after adventure. Don't let the number of episodes or chapters scare you off, this is a story unlike any other.
My favorite character is Trafalgar Law. I have tons of favorites but he's my number one pick. I like him so much that I even cosplay him.
I'm not saying watch it all tonight because that's impossible but give it a try if you haven't already. I guarantee you'll love it, I know I do.