Elf Sternberg

I def. like the meaty/umami taste of mushrooms in a tomato sauce -- someone suggested truffle, but if that's too $$$, I like to soak dried shiitake or porcini (Boletus sp.) in hot water until soft then add both the water and the chopped up mushrooms (possibly even processed in a food processor, but that goes against your tenet of simplicity). You can get dried mixed wild mushrooms in Slavic or Italian stores. Button/portobello mushrooms can be added for bulk, but their taste isn't robust enough to stand up on its own.

I've never had pancetta, but I imagine you could vary the taste a lot by varying the meat. My favourite, if possibly difficult to get, spicy Turkish sucuk sausage is phenomenal in pasta sauce. http://en.wikipedia.org/wiki/Soujouk.