A game party is great fun and really pretty easy to plan.
When I was in college, a big group of us from church got together every month for a game night party. It was so much fun, and I have a lot of great memories from those parties!
It is also an easy party idea that works for lots of ages, such as adults or for teen party ideas or tween party ideas, or even older kids.
While the concept would remain the same, the types of games may change a bit depending on the age of your party guests.
Board Games - if the games don't allow a bunch of players, have everyone switch tables and games after every game to intermingle.
Trivia Party Games are also fun, and can often work with larger groups of people.
Speaking of intermingling, games like bunco don't require much planning, are easy to learn and play, and are very fun.
You can include video games too - Rockband, Wii, Nintendo...just make sure you have enough for everyone to do, so it isn't just a couple of players with everyone else watching.