VectorPlot[ {-x,-y},{x,-1,1},{y,-1,1}]

VectorPlot[ { -x/Sqrt[x^2+y^2],-y/Sqrt[x^2+y^2]}, {x,-1,1}, {y,-1,1}]

VectorPlot3D[ {-y,x,-1/(x+y)}, {x,-1,1},{y,-1,1},{z,0,1}]