I am finishing writing a manuscript in collaboration with a dozen of colleagues. The paper is mainly theoretical, does not involved experimentation of any kind and is born from numerous discussions between all the collaborators (it is actually hard to tell when the project started). No one really took the lead in the project, at least not during the whole time (for meeting setup and so someone had to take the lead, but only temporary). In addition, the ten collaborators are coming from 6-7 different research groups and universities.
In such case, when everyone as more or less the exact same contribution, what is the best way to determine the author order on the paper, without making any diplomacy misstep?
PS: in my field , alphabetical order is really not common.
PS2: we do not have time for a 25 games croquet tournament...