Or how about one of my favorite all time missions: "Defeat 50 Nemesis Snipers in Founders Falls" These only appeared on one building and only during the games night time.
I remember there being at least six places where you could find Nemesis snipers at night. There was the building on the west side that had a Nemesis sniper about 2/3 of the way up on a ledge on the east side. To the south and a little east of that building, on the roof of a building overlooking the courtyard with a contact (Peter Steinitz? He had a tie-dye shirt, IIRC) in it was another Nemesis sniper spawn. To the east of that, on the 'island' that had the Founders Falls PPD station, there was a 'saddle' with a lower roof between two higher roofs; the north and south sides of the lower roof would alternate as spawn points for a Nemesis sniper. The separate building to the southeast of that spawn on the same 'island' would spawn a Nemesis sniper on either the NW or SW corner. The building on the west side of the road two blocks south of the hospital would spawn a Nemesis sniper on one of the lower canopies sticking out from the building, and there was another spawn point on the building on the west side of that road all the way to the south.
Thinking about it, it's a little disturbing that I actually
remember all of these, despite it being almost six months past the shutdown of the game, and even longer since the snipers were more than an occasional nuisance; I would get shot at by the Crey snipers on the east side a lot more often, given the flying route between the tram station and Icon back before all the trainers became costume-change contacts.