My DM once awarded my 13th level Warlock with a 9th-level spell slot as a boon for doing something heroic (the rest of the party also got something equally powerful).

The final battle came, and the good army was fighting against semi-immortal dark elves and their humongous semi-immortal demon of death and destruction and making the puppies cry.

I used that 9th-level slot to upcast Danse Macabre. 13 soldiers rose from the dead to answer my call.

Was it useful? Heck no. Was it hilarious? Absolutely.