My go-to icebreaker is "so, how do you know {party_host}?" Then share with them how you know {party_host}. That establishes a few things: 1) Instant connection

My go-to icebreaker is "so, how do you know {party_host}?" Then share with them how you know {party_host}. That establishes a few things: 1) Instant connection - we both know {party_host} 2) You learn a detail about them (occupation, hobby, hometown) 3) They learn a detail about you 4) You've told someone why you're there, so then you won't feel like everyone's questioning your presence 5) You've got a starting point for talking to more people (introduce this person to someone else you know, and/or they'll do likewise)