This one has always stood out to me, probably because it was the first Magic card I ever saw. It came as the promo for the 8ED starter kit, and the RG deck included
Enormous Baloth, which also resonated with me--as it clearly did with others in this thread. It's not the most elegant flavor text, but from the get-go I interpreted this text as an translation from Elvish rather than something this guy would actually say. Those layers of meaning, more than anything else, are what drew me to Magic.
More recently, this one really cracked me up. It reads like an Arrested Development gag, if Lucille Bluth was a vampire on Dominaria.