** Not your ordinary endless list - just what's number 1. Just the BEST.
2 Truths and 1 Lie.
I thought long and hard about this one and despite some other candidates, this activity due to its simplicity, personalization and structured language use - gets the vote. Plus, I've heard more good reports about this game than any other. It also has many variations.
Truths and a Lie - Each group/class member writes 2 true facts and one lie on a card. The teacher collects the cards and reads them aloud. The rest of the group/class tries to guess who it is and which fact is the lie. For lower level classes, put sentence fragments on the board and the students just finish them off.
The teacher should be the first to do this and should write his/her sentences on the board. Students can vote on which they think is the lie. This will clearly model the activity. Here are my own standards - can you guess correctly?
I wish I were more muscular.
I wish I could play a musical instrument.
I wish I had a dog.
I like using the 3 wishes variation for higher level students. This can become a full lesson where the students afterwards get their wishes granted. See the explanation here.
Also see the "snowball fight" variation
of this great icebreaker!
For more ideas, see this discussion on "The First Week"
and this one