In the spirit of "Shameless Self Promotion" I believe the following two mods fit into the "underdog" category:
1) Vivic Outdoor Mall at http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=6091. The first mod to ever use in-game full motion video as part of the gameplay while trying to keep such gameplay IAW most of the lore (balloon ride and "scuba" adventure). May be the ONLY mod that actually incorporates in-game full motion video (movies) as part of the gameplay - haven't bothered since to check if anyone else attempted that. Has many unique items for sale that you won't find anywhere else (i.e. new refreshments [new beer, wine, soft drink and spirits models IAW or enhancing to the lore], furnishings, interactive Vampire Soul Crystals, variety of new and unique textured placeable fireplaces [with "magic" delivery available], etc.). Only mod I know that has purchase inventories that change based upon the game month and game seasons so each revisit by your PC can produce literally scores of items for purchase that you haven't seen before (if in a new game month since last visit - food/beverages/hangable paintings/hangable tapestries). Incorporates lore "holidays" as part of the "gameplay" and many other unique and lore-correct/enhancing attributes. Provides both outside vendor stalls area and an Amusemant Attraction area with various vendors to provide "amusemants". Has periodic messages displayed to PC (normally once a game month) to inform PC of new items available. Has certain features that are only available at night (i.e. rotating spotlight, special lighting, different in-game night video for balloon ride, etc.). Works with both NoM and CoM but neither required. Has the following supplemental screenshots at this Flickr http://www.flickr.com/photos/8973190@N02/sets/72157603015654184. CATEGORY: Stores/Merchants as well as Amusemant Attractions - see full description at mod link. Also see this http://www.flickr.com/photos/8973190@N02/2132505191/sizes/o/in/set-72157603015654184/ for a quick overview of all it has to offer (non-CoM version, CoM version has even more). Mall is located outside, just NW of the Vivic Hlaalu canton (Ascadian Isles 1, -10 cell). Much care had been taken in the design to keep FPS manageable as well as eradicate any MW conflicts with other mods.
2) Sky City at http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=6365 (screenshots at link). Major quest mod that incorporates a flying city, religious strife through Daedric Prince plots and subplots, multiple quests taking place throughout Vvardenfell, optional end-mod scenarios based on PC interaction during gameplay, potential addition of new fast travel means that can be used on other parts of MW quests not part of this mod, new and unique ways to use existing animations (i.e. reference map that changes as you move Sky City locations, etc.), a time-sensitive storyline, and other things that make this mod unique in many ways. CATEGORY: Multiple-quest mod - see full description and screenshots at the link.
If you do decide to download these mods and once playing them feel they really shouldn't be "underdogs" anymore, VOTE on them at the mod links above.