I enjoy mapping and modding with UnrealEd since the old days of Unreal '98 and UT '99.
My most favorite UnrealEngine-based game is Deus Ex 1 !
My most favorite RPG Shooters, based on the X-Ray Engine, are all 3 games of S.T.A.L.K.E.R. (Shadow of Chernobyl, Clear Sky, Call of Pripyat), which I convert stuff from for Unreal Engine.
I also create old-school mods and maps for most known and lesser known UnrealEngine1-based games and also port stuff between them with UnrealEd and various tools. My UE1-Games installed and optimized are : Unreal v2.26f (1998) and v2.27 + RTNP Addon Pack (Return To Na Pali), Unreal Tournament 1999, Deus Ex v1112fm and GOTY Edition (2000), Wheel Of Time v3.33 (1999), Star Trek - Klingon Honor Guard v1.1 (1998), Star Trek DS9 - The Fallen (2000), Rune (2000), Undying (2001).
Plus I own thousands of user-made community mods and maps ever created for all these games.
Yes, this is strictly Unreal Old School!!