Really depends on what your interests are. If it's more ride based, I'd say USH. If you just want a very in depth Studio Tour, I'd maybe say WB.
If you're into Horror in general, I'd recommend what's nicknamed "Horror alley" in Burbank, where the stores Dark Delicacies (books and gifts, and often does signings with famous horror writers), Halloweentown (the main store, not the costume store--overpriced merch, but it's really well themed), and Mystic Museum/Bearded Lady (the stores are side by side and feature creepy antique oddities)/Slashback Video (an upcharge exhibit, but a must if you're into 80s horror). Free admission to all except Slashback! And the local favorite bakery, Porto's, is also right there near Dark Delicasies (and always has a massive line!).
I'd also add if you can get to it, The Grove is even better than The Americana, because The Grove also has the historic Farmer's Market (open daily), which is really a piece of old LA history and is a unique experience. Come hungry!
And if you want something relaxing, head to some of our bontanical gardens. The Huntington is immaculate, Descanso Gardens has a more forest feel, and LA Arboretum is a mix of both, and includes feral peacocks that roam around.