Yeah. Chopper wins on creativity for his DF powers. While he isn't physically strong (aside from Monster Point.) it doesn't necessarily mean it's a bad thing. He's a Doctor. He's far more concerned about learning than he is at fighting (same can be said for Robin. Kinda.)
However he seems to be doing well in various Rumble Ball forms which I imagine will be expanded on in the future.
Of course for Physical strength he has Monster form which is pretty impressive, even more so when you consider it was actually seemingly doing something against Sentomaru compared to Luffy whom couldn't.
Although I don't want to see that controlled any time soon. Once it is it'll immediately be nerfed so that Luffy, Zoro and Sanji are stronger than it. Better to be just used as a last ditch effort.
Although I wouldn't mind Chopper being SEEN fighting a bit more. His last proper fight was when? W7? Even that he required to use Monster. So maybe even as back as Skypiea. Not counting his TB fight since it was with Robin and was cut short for Odz (grrr)
But personally I think some of the better and more interesting DFs are the non logia ones. Robin's and Luffy's are obviously cool, but imagine the ones like Miss Valentine. If she so wished she coulda probably floated up into the air and then increased her weight so much she could defeat a Kumabot or whatever. Would be amusing.
Lamest is probably Brook's in that it's more or less just a plot device and isn't used in fighting (That we know of. Who knows if it could be.)