Manipulate[Plot[Sin[x(1+a x)],{x,0,6}],{a,0,2}]

Manipulate[
Graphics[Polygon[pt],PlotRange->2],{{pt,{{0,0},{1,0},{1,1},{0,1},{1,-1}}},Locator,LocatorAutoCreate->True}]

Manipulate[
pt,{{pt,{{0,0},{1,0},{1,1},{0,1},{1,-1}}},Locator,LocatorAutoCreate->True}]

Manipulate[
{pt[[2]], Graphics[Polygon[pt],PlotRange->2]},{{pt,{{0,0},{1,0},{1,1},{0,1},{1,-1}}},Locator,LocatorAutoCreate->True}]