I've been wracking my brains all day, but I can't remember where I read this fic.
Somehow it's discovered that Rodney has absolutely brilliant ideas immediately after (or during) sex. John is a practical and rather desperate man, especially in looming-death-situations, so he ends up with the rather twisted/shocking/hillarious/what have you habit of getting Rodney off in the interest of disarming-this-bomb-right-this-second-c'mon-Rodney-holy-shit-we're-gonna-die/come-up-with-a-brilliant-idea-RIGHT NOW-or-the-Wraith-will-kill-us resolutions. ...things ensue. I can't remember exactly what - which is the main reason I've been trying to find this fic.
Does any of this ring a bell?
eta: Found, many thanks for
b3ri ! It was
Tango by astolat.