My game is modded from here to Malachor 5, and this is by no means and inclusive list.
RedHawke's item packs - insanely powerful items, but definitely fun. They way they're integrated into the Endar Spire makes it aqctually fit with the story.
Red Hawke's Ord Mantell - Two sidequests and some brutal fights for your higher-level/modded out characters. The reskinning and fitting-together of multiple locations is also a very tough task.
Manaan door relief and Manaan Fish fest - I listed them as a set since they work in dandem to relive the greatest annoyances of Manaan, namely the insanely slow pace of the underwater sequence and the constantly scolding doors at the docking bay.
MECK's Jabba's Palace - The anachronistic dialogue is my only complaint here. Otherwise, it's a nifty little sidequest with an inventive use of reskins.