Depends on the crowd, I usually play it by ear

and if in doubt then leave it out!. Sometimes you can stay too safe and each gig becomes like a Radio 1 Playlist

with you following one track with the same one at every gig, but if its a different crowd each time, and it fills the dancefloor then what the hell!.
There are the more obvious - I mean, I wouldn't play the Sex Pistols or Marilyn Manson at a function where 80% of the audience were in their 50's or 60's, then again I wouldn't play Max Bygraves at a high school disco or an 18th.
Also look out for obvious tasteless tracks for any circumstances. Playing New York New York on 9/11 could have been taken in 2 contexts, so better not taking the risk, as was my own claim to fame and embarrassing moment, when a Roadie played "You'll never walk alone" at the end of a gig for the disabled!.
Although having said that, a very emotional young girl wanted me to dedicate a track for her boyfriend who had been killed recently in a motorcycle accident. Hmmm the track was "Stayin' Alive"

. What would you have done?.