Here are some Hunter x Hunter references in other anime & manga:
https://www.reddit.com/r/HunterXHunter/comments/7cnl8l/hxh_references_in_anime/dprpysk
https://www.reddit.com/r/HunterXHunter/comments/7cnl8l/hxh_references_in_anime/dprpysk
From Nisekoi
From Danganronpa 3
Good ole Gintoki speaking truth:
Mahou Shoujo Site in chapter 109 references Togashi's infamous novel page in Hunter x Hunter chapter 388.
In the recent chapter (+12) of Lycopene, there again references (parodies) Hunter x Hunter's novel page from chapter 388.
https://shonenjumpplus.com/episode/10834108156643577004
https://shonenjumpplus.com/episode/10834108156643577004
From Shonen Jump 2016 Issue 20, Isobe Isobee Monogatari reference parodies Hunter x Hunter for its color page.