Icebreakers are the best at getting strangers to know each other and not feel so awkward when they are first put in a room together. There are icebreakers that help people learn to work together in teams and are perfect for Corporate Events, but in a smaller or social group you often just want them to loosen up and give them a gentle push to open up and make a new friend.
One of the best games I have seen to help with this is a variation on Bingo.
Give each person a "Bingo" card you have made up for the occasion. They don't need to say "Bingo" at the top. You can use any word that fits with the theme of the event. I have several blank ones for sale that would work for many different types of get-togethers. They do not need to be a 5x5 grid either. Choose the number of squares in the grid based on the size of your group.
On each square you want to write something about the people in the room. Be careful that you are not being unflattering or too personal. So you might put something like:
Is wearing white socks
Is wearing high heels
Is wearing brown shoes
Is wearing red
You can get a bit more challenging if you want by adding in a few squares with people's names.
Each player has to get the person that meets the description to sign that square.
Then it is up to you if you want to make them fill out all squares or just a row or some other typical Bingo pattern. It will depend on the size of your group and the amount of time you have for this activity. This should get everyone up and moving around and interacting. If you notice that they are not having fun or it is dragging out or turning clique-ish, then at that point step in and say something like "ok, one minute left" and end the game before the task is completed. Award the prize to the one that came the closest to completing the task.
As always have some sort of small prize for the winner.