Last few years I observed that the biggest of all debates that occur during the course of a project is during the sizing of the stories. Most of the times in the teams I have worked we had fibonacci or t-shirt sizing and sometimes 1,2,4,8. We humans are not so good when we deal with numbers which are closely spaced. T-shirt sizes are also closely spaced S,M,L loosely translates to 38, 40, 42. This leads to people arguing whether some stories is of 2 or 3 points or Small or medium size and gets into tasking and implementation details to get the right size.
When I was thinking about a better method for sizing, I read in some feed that a person tried to use reptile sizes like gecko, iguana, alligator and komodo. Each different in size and class from the other. I thought, let me also give a try and then came up with Scooter, Car and Bus for the sizes with Bicycle and Trailer as outliers (similar to XS or XL in t-shirt sizes). To my surprise it was too easy for people to slot the stories into one of these sizes and there were very few arguments and a simple task break down of a story gave a picture of the size/complexity. This worked much better than S,M,L or 1,2,3,5,8.