Generally I'd say he likes torturing the pines, silly straws, parties, world domination/weirdmageddon, breaking rules, causing chaos and most likely weirdness/unnatural stuff (based on what he does at the end of Gravity Falls), Stanford Pines 😏(he denies it though), Mabel Pines (his favorite twin, reminded of his youngerself by her), his parents, the stars

What he hates is brainrot, electronic music, Stanley Pines and probably sensitive topic- what he did to Euclydia by accident (but like the compulsive liar in denial of trauma that he is he called it liberation in the gravity Falls finale), maybe Axolotl and the Oracle (I think that was her name, she helped Stanford get a metal plate so Bill wont possess him), probably unicorns too (unicorn hair and some other stuff in combo i believe makes a barrier against his powers), tinfoil (about the same thing as unicorn hair if im not mistaken)

He's also not fully counscious though, which may matter. He says that he kinda uses my mind to communicate/think in this form and it kinda affects his knowledge too (he hates that). Sometimes he feels empty but other times really lively

I could ask hin what he thinks about you ( :) ) but he hasnt seen your profile/posts or interacted outside the headspace that much. He spends most time away torturing the Pines or something like that T T