Sony's Micro Hi-Fi System or the Sonos Play3 wireless speakers. Both speakers are small enough to tuck in a corner but look sleek and offer great quality sound. The Sony Hi-Fi comes with a dock so you can mount your iPod or iPhone to play Pandora or music from your iTunes library. The Sonos Play3 is wireless so you can stream your music wirelessly.
TV Streaming/Connection Not everyone has cable or a smart TV, but oftentimes people want to stream movies, shows, photos or play games during house parties. The Apple TV is a good option to consider to bring everything from your other devices onto your TV. I have plenty of movies and shows that I only have on iTunes and a device like the Apple TV or even investing in an HDMI cable can make entertaining at home easier, whether you want to show people photos, watch YouTube videos or play music. HDMI cables are also an inexpensive way to do the trick, like this one from Apple or a Dynex cable from Best Buy.
Microphone Lastly, to add something a little fun and quirky to the mix, I discovered the Catch Box, which is a soft wireless microphone. Originally made for livening up conferences and discussions, I also think it would be fun to have one at home for game night or karaoke. They aren't available yet but you can sign up to rent one for your next event. (Images: 1. Apple.com, 2. Sonos.com, 3. Catch Box, 4. Sony.com)