This one can be played with as many players as you like.  You're only limited by the number of strangers you can get to participate.   Decide what the pot will be and how many digits count out of the 10 digits available in any phone number (we usually take just the last 7) and which number from the phone will be used (I like taking the last number called or maybe the third to last called just to ensure randomness).  Then you get the phone numbers from your participants and compare cell phone poker hands. 

 

This one is a classic bar bet. 

 

You also might end up with more phone numbers than you started with!