I realize that this thread does not exist and it should, so I will make it. Let's make this a discussion and not a character fan base. Make your lists and I will update mine to changes. Remember, only really strong characters that actually matter, no deceased and non-canon characters unless used to compare the important ones.
I've actually taken quite a lot of time thinking about this with the information given and I know some will disagree, but that's what forums are for heh? Also these are assumptions because Oda loves to confuse us a lot so these might not make sense.
SO far I've come up with a list of a list of strongest One Piece characters going from number 1-6. The numbers to the right indicate the power level of the strongest character – maxing out on 10.00 and going down from there -- so to compare them to others.
THE TOP SIX:
1. Shanks (10.00)
2. Kaido (9.95)
3. Dragon (9.93)
4. Blackbeard (9.80)
5. Akainu (9.79)
6. Big Mom (9.64)
You can also use the power levels of Fukuro (Doriki) if you wish: Rob Lucci being at 4000 during Enies Lobby.
I only have these six because it is so damn hard getting these others to be listed conclusively (it's not as if the first six are definite):
REALLY STRONG: (no particular order)
Fujitora (He is kinda my 7th pick)
ALMOST REALLY STRONG: (no particular order)
JUST QUITE NOT THERE YET:
Jesus Burdgess (Haven't been impressed by him)
MY JUSTIFICATION FOR TOP 6: Shanks at the moment just seems to be the king. He is not afraid of anyone and avoided Kaido somehow, plus the Haki against Akainu. Kaido to me seems to be the only guy (at the moment Dec 12th, 14) who can take down Shanks. We definitely can all agree Blackbeard is probably is still developing his powers. Eventually we have Dragon. Such a mystery, but he has to be Yonko level at least, and with the power of manipulation of weather is some way definitely, he is unreachable. As for Blackbeard. Two OP Devil Fruits. Afterwards we hit Akainu. He has had a lot of time to improve and I think he is at his prime at the moment (well has to for the sake of the story hehehe). He would really give Blackbeard a tough time cause mind you, Sengoku did it and he was way past his best. Akainu is Yonko level no doubt and if he found Big Mom, I think he could take her down.
Remember, these are just gut feelings and assumptions, so there is no way that I can know for sure that Akainu is stronger than Big Mom.