For discontinued creams, I would go with Noxzema Lather Shave. When I started this hobby, it had already been discontinued, but a guy offered a NOS tube for sale and I bought it. It was fabulous. I will also include the entire line of Coates' creams, with the Tea Tree in particular being both a great performer and an utterly unique scent. Yes, I know you may still be able to nab some of those tiny travel tubes that the dude found in a warehouse, but it's not the same.
For discontinued soaps, hmmm, where to start? I miss the Saint Charles Shave soaps. I used them up quickly, but miss the unique scents, especially Refined. I have a couple of tins of Fairway, but will miss that one too when they're done. Though I still have 3/4 of a stick of Irisch Moos, I miss it since it was completely discontinued and that it was never offered as a puck. Now that they've reformulated Tabac too, well, that's even more loss to consider. I also miss La Toja Manantiales in the wooden bowl with cork lid. The biggest mistake I've made in shaving is 3017ing the one I had. I still think the La Toja stick is the best soap in production, but man, who can get excited about a stick?