/ʂw/ > /f/
In the town I’m in (Mianning), there’s been a particularly disturbing and/or hilarious sound change in their variety of Southwestern Mandarin, namely /ʂw/ > /f/, the result of which is that, e.g., ‘drink water’ (喝水) is /xo⁵⁵ fei⁵⁵/, ‘fun’ (好耍) is /xao⁵⁵ fa⁵⁵/, and ‘read’ (看书) is /kʰæn²¹ fu⁵⁵/.
This sound change, as I hope all my Ling 130 students will recall, is a kind of fusion, since /f/ retains the manner of articulation from the fricative /ʂ/, and the labial place of articulation from /w/.