I love Delta Green. I rarely get to run it, but Delta Green and its sequel, Countdown have more than earned their place on my game bookshelf. This is thanks to its modern horror take on the Chtulhu mythos and compelling scenarios like "The Night Floors", in which a certain play dooms an entire apartment building.
A few years ago I picked up Weird War II by Pinnacle Entertainment Group to supplement my The Day After Ragnarok book with World War II Savage Worlds rules. The rules were fine -- it helped with the demolitions skill and gave me access to an armory of guns and vehicles -- but just wasn't weird enough for my taste. The history of the weird war was pretty much the same as the history of our war; the weirdness was at the edges and never infected the larger narrative in the way that, say, Delta Green did.