Sins and Virtues by Jane Carnell http://hjc.akicif.net/SinsandVirtuesTOC.html
Comrades by Jane Carnell http://hjc.akicif.net/ComradesInArms.html
Both of these excellent stories are Hawkeye/Mulcahy. Sins and Virtues follows their relationship after returning home and deals with Mulcahy's deafness and difficulties reconciling his religious beliefs with his growing relationship with Hawkeye. It is well-researched and well-written. Comrades is a much shorter moment inspired by the episode Comrades in Arms," but with Mulcahy in the place of Houlihan. Both include sexual scenes, although the former much more than the latter. The author has written many from MASH fics, but many of the links on her website are broken.
Runaway Train by aura218 https://archiveofourown.org/works/327148
Another fic inspired by Comrades in Arms," Runaway Train does not shy away from the possibility of rape in combat situations, dealing bluntly with the topic from BJ's point of view. It is an excellent character study of Hawkeye, BJ, and (to a lesser extent) Houlihan and I highly recommend it. This fic is not sexually graphic, but contains a lot of discussion about rape recovery and probably deserves a higher rating than the T (teen) that is has.