I don't think a trade can be made with damaged goods (Kesler, Spezza, Green, Letang) because it could come out really badly for one side.
Of these guys, I'd rank them as:
Just for discussion... that's the order I'd want them in.
For me... the consistent guy to consider (as horrorfan suggests) is Jon Toews. He's rock-steady and a FOW-monster.
The other team has a boatload of awesome defensemen, enough to part with any.
So my trade would be:
Defensemen of your choice.
(and if the team with the great D absolutely loves one of his guys, he just says "except for _____")
That's my trade.
And I like it... because I'd be willing to make it from either side.
It's a win-win, because the team getting Toews upgrade his centers by a good amount & downgrades his awesome D by just a bit.
The team getting the D upgrades his defense by a good amount & downgrades his awesome C by just a bit.