It's a bit of a quandary - my favourite ever Dons player seen in the flesh is Eoin Jess, but when you say 'skilful' I think of 'flair' and I'd maybe have to say Zero.
Jess would win if the topic was 'classiest' with the way he could just stand folk up and ghost past with no dramas and nestle the ball top corner - possibly only Niall McGinn has come close to that for us since.
Elsewhere - Ronaldinho for Barca. Sheer unadulterated joy - both from him and for the people lucky enough to be watching.