liked and played most of the vanilla maps, all time most played maps of those were probably compound, depot and verloc.
liked quite a few of the UMP2 maps as well, especially the suk stronghold, dm_bw ascension, strange but fun map, buggy too, racing to the top, if you shot off a human's head with the speargun, the head would be flying around the map forever at high speed. another good one was this beach like place with water, a submarine you could swim into and lightning strikes overhead.