(abt the questions) oh, maybe the favorite monster? and a favorite sword/armor?
Oh boy, I'm a shameless monster enthusiast so this is gonna be a long question.
I adore the leshen. The design of it is beautiful and its moveset is SO COOL! I was really happy that I could solve the In the Heart of the Woods quest without killing the ancient leshen because they're just so neat! Their lore is also interesting, what with them being the protectors of the forest - we need them around in the modern day IMO.
The hym is AMAZING. I'm a slut for shadow monsters and it's great to see one in Witcher 3. Shame there is only one in the entire game, though. Kinda sucks that it's not sapient and feeds on pain and guilt of its host, because otherwise I could do a lot with the concept.
The silver basilisk, Iocaste, is beautiful and I'm glad that I had the option to spare her. Hope that the Count manages to restore the species somehow.
The shaelmaars are cute, and it was really satisfying that Geralt can spare the one on the arena and then give Anna Henrietta a stern talking-to about the dangers of bringing it near the public. I felt so bad for how it was treated - it was probably scared and confused by the bells at its tail. If that ain't animal cruelty, I don't know what it is. For shame, Annarietta.
I absolutely love all vampires, which should come as no surprise whatsoever. The katakans are ADORABLE and I'd love to hug one. Precious batty babs. Ekimmaras, too, but katakans are the ones who can hold a conversation. I like the bruxas in Blood and Wine, though it's a shame that there's no way to spare the one in Corvo Bianco. It's kinda funny how all the ones guarding treasure around the map can't do shit to me during the day so I can just walk up, take the loot, and leave without even needing to fight them.
Dettlaff's final form is KICKASS (and also kinda hot if you ignore the "literally blinded by pain/grief/rage" implications of the design not having eyes) but I can never bring myself to fight him.
Tesham Mutna armour, New Moon armour, and School of the Cat (excluding the hood), though I like the Ornate Robe you find in the Van Everec estate as well because it's red, offers decent protection, and exposes so much neck that I wore it a lot during B&W for funsies like "Hey vampires! Come get y'all's juice!"
I'M SUCH A HO FOR SWORDS. I FILLED ALL THE DISPLAY STANDS AT CORVO BIANCO. I PAUSED THE RACE WITH O'DIMM WHERE MY VERY SOUL WAS AT STAKE JUST TO GRAB THAT SWEET SWEET VENOMOUS VIPER SCHOOL SWORD.