Do any of you have sets that you think are really under appreciated or that you were unexpectedly impressed by, such as a great set from a generally disparaged theme or a set that is generally overshadowed my other more well regarded sets? I'm not talking about your favorite sets of all time, but a set from some random theme that you really like or one of your less favorite sets that you still consider an integral part of your collection (i.e. your fifth favorite set).
This question was prompted because I randomly decided to check out some of the western themed LEGO sets. I didn't really have that much to spend, so I decided to pick up a medium sized set and bought a reasonably priced Gold City Junction (6765) off of ebay. Anyway, after putting it together I was really floored with how well they captured the wild west aesthetic while including a bunch of really fun play features in a relatively small set. I was really surprised by how good the set was since it didn't seem to be one the most popular sets in the theme (evidence by the fact that it was not re-released). This got me to thinking about more recent sets that I was really impressed with despite relatively low expectations, such as the Ultra-Drill Walker (7649) because of its inclusion in the Mars Mission theme.
Anyway, I would be interested to people's opinions about sets they think are hidden gems.