Sorry for the somewhat late reply... I just found this forum and joined.
I have two Figure 8 puffers, which I find endlessly entertaining and adorable. Their names are Lucky and Plucky. Lucky used to be the smaller and less dominant one, but that has all somehow reversed in the past 6 months.
Anyway, I'll cut to the chase.
I have experimented with keeping sailfin mollies with the puffers. On average, a sailfin molly will last about 1 month with the puffers, before getting its sailfin and/or tail "trimmed" by the puffers. This seems to be related to the mollies becoming more familiar with the puffers, and more aggressive with the puffers. I think the puffers bite the mollies' fins just to keep them in line. The mollies generally try to steal the food from the puffers, which is futile in most cases, as I feed the puffers snails most often. The puffers have, a few times, tried to steal the sinking pellets that I usually feed to the mollies. But when they take the pellets into their mouths, they spit them out immediately.
I don't keep any other kinds of fish with my Figure 8 puffers any more. As an aside, the mollies with the badly-bitten fins generally learned to respect and stay away from the puffers. (But not always.) One thing surprised me, the molly which turned out to be the most aggressive with the puffers was a female. This crazy molly managed to scare the puffers so they didn't bite her fins any more. Occasionally I see this degree of aggressiveness in female mollies, though it always seems to be a reaction to aggressiveness (so I'm guessing it's just self-defense.) I digress, but I had a super-aggressive, large dalmatian sailfin molly before, that terrorized everything in the tank with him... That is, until he terrorized a particular female for a couple weeks, then she turned the tables on him. My wife and I found the turn of events to be somewhat amusing.
Something somewhat comical that Plucky does now is, when she sees me, she will often come to the front of the tank and snap her teeth as if she's trying to bite through the glass.
I'll post later about the most amusing thing I've ever seen these two puffers do.