One thing that I learned early on is how much a surprise can change everything. It takes a tiny bit more planning but the element of surprise is what makes things fun. I try to incorporate that idea into the parties I throw. If you choose just a few party ideas of things you were planning on doing anyway but add the element of surprise, it ends up being the most memorable part of the party. Whether that means there is a surprise guest or balloons fall from the ceiling or an accordion player pops out in the middle of the party the extra surprise is entertaining.
For a dinner party once I sent the invitations in a cryptic bottle. Each one was typed by hand on an old typewriter and they guest were told they wouldn’t find out the location until they day of the party where they would receive the clue.