Peek A Who
A sheet or tarp big enough for half of your group to hide behind.
Split the group into two teams. The group must either be introduced or be somewhat familiar with the other names in the group (although this is a good game to quickly reinforce name/face recognition). Each team sits behind one side of the sheet so that they are out of the view of the other side. One person from each side will sit facing the sheet. When the sheet is lowered, the team that says the name of the person on the opposite side first gets that player on their team. The game ends when everyone is on the same side.