In reply to richardsavery:
Definitely the Mont Pelvoux traverse in the Ecrins, that might be the best of them all. It's certainly the best one I've done. In many ways it is the perfect mountaineering route. it's got glacier, snow couloir, abseils, committment, routefinding and scrambling. It is probably PD+ though.
I also really enjoyed the Hohlaubgrat on the Allalinhorn and The Weissmies traverse.
P.S. Isn't the fletschorn-Lagginhorn AD?