Digitalis is not a spell in Harry Potter.
No one it isn't real.
Harry Potter's favorite spell was Expelliarmus (disarming spell) but he also used Stupefy (stunning spell) a lot.
Stupefy.
Mobiliarabus
Expelliarmus.
Accio
Expecto Patronum
Petrificus totalis
In the fourth book, Harry used the spell, Diffindo, to rip Cedric Diggory.
The spell that Harry Potter used to cause Draco Malfoy to bleed continuously in the bathroom duel scene of "Harry Potter and the Half-Blood Prince" is called "sectumsempra".
The spell Expecto Patronum is used for calling your Patronus in Harry Potter.
Lomus or something like that