I have yet to run into a circle that didn't enjoy seeing someone pull off simple tiltless tricks.
Though like everyone else said, generally tone down the tricks, but things that impress the crowd a lot are.
Aerials (always gets the eye)
Around the Worlds (always gets em)
Duckigns (same)
and of course the ultimate crowd pleaser!
The pendulum
But the Hacky circle is a place to kick and try to get hack, so generally keep the strings very short jsut quick bursts. Even give props to the other people or ask if to give some small tips. heck even push them like "Can you do a toe stall or a flying clipper? How bout a dragonfly?" simple tricks and if they hit it they'll be hooked
But I'll shut up now since everyone said what I said I think
Peace,