The Möbius strip, as a parametric surface.
\documentclass[border=10pt]{standalone}\usepackage[inline]{asymptote}\begin{document}\begin{asy}[width=\the\linewidth,inline=true]settings.outformat="pdf";settings.render=0;settings.prc=false;import graph3;size(200,IgnoreAspect);size3(200,IgnoreAspect);currentprojection=orthographic(camera=(1.5,0.3,2),up=Z,target=(0.5,0,0),zoom=0.8);real r=2, w=1;real x(real u, real v){return (r+v/2*cos(3pi*u))*cos(2pi*u);};real y(real u, real v){return (r+v/2*cos(3pi*u))*sin(2pi*u);};real z(real u, real v){return (v/2*sin(3pi*u));};triple f(pair p){return (x(p.x,p.y),y(p.x,p.y),z(p.x,p.y));};draw(surface(f,(0,-w),(1,w),nu=9,Spline),orange);\end{asy}\end{document}
Source: TeX.SE