The obvious answer is MWF, but I also recently discovered that Williams (tallow) is a completely different soap with soft water. We have had work done in our cellar and we disconnected our water softener. Yesterday's shave with Williams was a bust. Probably the worst I have ever had. (You all know that I am a Vintage Williams Junkie). This morning, before shaving, I reinstalled the water softener. Low and behold, my beloved Williams came through with flying colors. Any other soaps in your arsenal that are finicky enough that soft water is a must?