Containment Area in 1¼h
Last week I finally managed to beat this map with 100% kills and no use of savegames. I was very happy to get this one done as I have long believed it impossible, well, not exactly impossible but far beyond my patience at least. Dying after an hour's careful play is too discouraging. But it turns out the parts that I thought required too much luck (mostly the cyberdemon fights) can also be made largely risk-free.
See also Containment Area, the last time I was playing it.