In all my years of gaming, the one thing I've always wanted to do with Sending is to go somewhere private around 2am and just scream "AAAAAAAAAAAAAHHHHHHHHH!" at the BBEG. 25 times. Every scream just a full breath of air, as long and as loud as you can without blowing out your vocal cords.The spell which alters our setting the most is Sending. It's not a "bad" spell but it fundamentally changes how your PCs will achieve quests they're on. It's a rare adventuring day where we don't conclude the day with one or more Sending spells to allies, or information brokers, or even enemies.
With enough slots, or a Warlock taking short rests over the night, you might even make the BBEG exhausted and down some spell slots of his own for the final confrontation.
