Word-play.
I must not be the only person who has this irrational fondness of certain words, truly by the virtue of how they sound and the way they roll off your tongue. To begin with, I really like rhyming phrases, for example: hustle and bustle, hither and thither. I love words like ease, cease or seize, ones of very few single-syllabled words you don't rush into - you take time to go through the vowels, not merely leap on the word in hurry to arrive to the next word. I like through because of the 'th'; the intricate way to produce the sound, teasing your tongue just slightly between your teeth, exhaling some air, and the sound it produces has an airy, feather-light quality to it. I like words that have the tricky 'double-s' endings like assists or consists because it's really tricky to pronounce; the 's' kind of stops briefly, but then you pronounce another 's' again just as briefly. It's hard to pronounce it correctly, but when done right it sounds beautiful.
This is also the reason why I tend to pick the word perhaps over maybe, or probably, or any other words with equivalent meanings. Because perhaps, that is how I always imagine how hopes, chances, and promises will take form in sound - it starts with p, the dead, close-mouthed consonant, then you go through its two vowels separated by the tricky r and the airy h, and right when you thought the word would end the same way it started, with the same dead, close-mouthed consonant, it gives you the subtle hissing, perhaps slightly buzzing, s, and just like hopes, chances, and promises, it doesn't leave you right away, it lingers.