Straight from Nonna's Kitchen!
The most traditional, evergreen Italian way to serve Pappardelle is with a game stew or sauce. Wild boar, deer, rabbit, pheasant, everything is good. The most famous recipe comes from Tuscany and is the "Pappardelle sulla Lepre" (I have never understood the reason of this name since you're supposed to put the hare stew on the pappardelle and not viceversa:D )
Generally speaking, the meat is marinated with wine, vegetables and herbs and then stewed, adding tomatoes or not according to the various recipes and the type of meat you use. To make a sauce, the meat is boned and chopped after cooking, the vegetables sieved and more tomato and/or butter or cream is added.
Another traditional recipe (and, maybe, my favourite one) are the Pappardelle con Funghi Porcini.
I love making this recipe in the simplest way: chopped garlic gently fried in Extravergine oil, then sliced fresh Porcini are added and sauteed for 5-6 mins (they must remain a little crunchy), finally salt, pepper and a pinch of freshly chopped parsley is added and it's done. Since some people find this version too dry, sometimes I add some fresh cream and grated parmesan.
BTW: I have a curiosity. Maybe I'm silly to ask this, but are fresh Porcini available in US? I've never found them in the other European countries...