I don't think I have a single favorite word, because I hate catchphrases. I've known quite a few people who had noticeable go-to words, and it always left a bad taste with me. I don't think it's because they chose the wrong words (although the girl who said "groovy" ten times a day could have made a better choice), but because any word will seem stale if overused.
My favorite words are creative variations built around a common theme. For example, a while ago I greeted a friend with "hey pigfucker" in public, and it pissed him off. Red face, "people can hear you!", it was awesome. I knew I was onto something, but I couldn't just call him "pigfucker" again, because that's old news. Instead, I made a list of alliterative pigfucker synonyms, like Swine Stuffer, Hog Humper and Pork Pumper. I think I had about ten in total. After a while, he'd be angry-laughing as soon as he saw me, before I even opened my mouth.
I think I was more proud of "Boar Booty Basher" than I was of graduating college.
In my native language, Polish I have several: 'kurwa' - it's just so... juicy and emotional, arguably the best curse in the world. Another one is 'ciepło' which means 'warmth' - it just sounds... warm, soft and cozy.
In English I like 'to flabbergast' and some other words I can't recall right now. I'm not a fan of English swear words tbh.
Hmmm I see an interesting pattern emerging here - do all ENTPs have an inbuilt love of swearing?
Personally I use the word 'fuck' liberally - I don't buy the old adage about how swearing is for those with limited vocabularies, it's a great word for adding stress to a sentence! I also use the word 'cunt' occasionally but tend to be far more tactful with who I use it around - for example I have a couple of friends who I will greet with 'awright cuntface' or 'how's it hanging cuntyballs' (these are expressions of affection I swear!), I also have other friends I would never dream of greeting them in such a way because they would interpret it in a way not intended. I also enjoy using expressions which have a degree of vulgarity attached to them - e.g. "I'm sweating like a whore in Game of Thrones".
Anyway... back to the original question... I wouldn't say I have a favourite word per se but I definitely have a tendency to use longer, more abstract words. Right now 'quintessential', 'incandescent' and 'intrinsically' seem to be featuring in my vocabulary perhaps more than they should. I also have a tendency to appropriate Marxist terminology and use these words outwith their original context - e.g. "I have a laissez-faire attitude towards brushing my teeth in the mornings".