Hi I was just wondering if an oppent has a unique card ,eg litlle finger, could I then play little finger ?

The rules prevent you from marshaling, putting into play (note that only events are "played") or taking control of a unique card if:

- you already own (you own cards that started in your deck) or control a card with the same name in play (though if you both own and control it, you may marshal it or put it into play as a duplicate)

- there is a card with the same name in your dead pile

If your opponent owns and controls that copy of Littlefinger, it doesn't stop you from marshaling yours (or putting it into play). If you own that copy (and your opponent somehow took control of it - no card makes it possible for Littlefinger, but Yoren would work with a cheaper unique), then it does. Likewise, if you have taken control of a copy of Littlefinger owned by your opponent, it also stops you.

Perfect thank you

You're welcome.