Ok I'm going to be annoying and list around a dozen or so riders who I think can go well here:
Bardet: He's along with Nibali the GC contender who races at the Ardennes most and he has an ok kick. He'll be willing to try make up some time and in the process could nab the stage victory. Vuillermoz has also got a good chance here.
Froome: If some of the other GC contenders attack he's sure to follow and has a good sprint.
Gallopin: Showed great form on the Mur De Huy and Lotto seem to be riding on a wave of confidence. My pick for the stage.
GVA: An outsider, but one who must be considered.
JROD: He's already been mentioned by others as to why he can win, so i'm not going to explain why. Same for Valverde.
Simon Yates: Has a better flat sprint than Adam and is on good form.
Stybar: This stage could suit him and he can tough it out. He cannot be underestimated.
https://www.youtube.com/watch?v=uufAdshol4k From 19:28 it shows his SB win from this year. Uran and Kwiatowski could also win the stage for EQS.
Mollema: Should attempt to target this stage. Canny and has a nice sprint.
Rui Cost: Same as Mollema, but probably better suited to the last few hundred metres.
Martin: Has showed he is a perennial threat on climbs like these. I have confidence in him and with Haas and Hesjedal he has great hilly support.
Contador: Might want to test the legs and rode well here in 2011. Sagan I think will also be in the frame.
Other riders who could feature include: Gesink, Meintjes, Navarro. From a break/ early attack-EBH, Chavanel, Huzarski, Edet, Jungels, Voeckler, Wellens, Geschke,