Dead simple signed distance function ray marcher written in as few characters of code as possible. Clearly, the rendered image is not that cool, but it was fun.
Somewhat minimized source code (1746 characters)
#include <bits/stdc++.h>
#define O operator
#define R return
using I=int;using D=double;auto Mi=fminf,Ma=fmaxf;auto Ab=fabsf,Sq=sqrtf;struct
V{D x,y,z;V(D v=0){x=y=z=v;}V(D a,D b,D c){x=a;y=b;z=c;}D L(){R Sq(x*x+y*y+z*z);
}V O+(V o){R{x+o.x,y+o.y,z+o.z};}V O-(V o){R{x-o.x,y-o.y,z-o.z};}V O/(V o){R{x/o
.x,y/o.y,z/o.z};}V O*(D s){R{x*s,y*s,z*s};}V O*(V o){R{y*o.z-z*o.y,z*o.x-x*o.z,x
*o.y-y*o.x};}D dot(V o){R x*o.x+y*o.y+z*o.z;}V O!(){R*this/V(L());}};D C(D v,D l
,D h){R Mi(h,Ma(l,v));}D X(D l,D h,D t){R(1-t)*l+t*h;}D R1(){R D(rand())/
RAND_MAX;}D uni(D d,D b,D k){D h=C(.5+.5*(b-d)/k,0,1);R X(b,d,h)-k*h*(1-h);}D
dif(D b,D d,D k){D h=C(.5-.5*(b+d)/k,0,1);R X(b,-d,h)+k*h*(1-h);}D sdbox(V p,V b
){R V(Ma(Ab(p.x)-b.x,0),Ma(Ab(p.y)-b.y,0),Ma(Ab(p.z)-b.z,0)).L();}D S(V p,V&c){D
td=Mi(uni(dif(p.L()-.45,V(p.x,p.y,0).L()-.2,.1),sdbox(p-V(.33,-.3,.3),V(.05,.5,
.05))-.1,.15),Mi(sdbox(p-V(.9,-.7,.25),V(.05,.1,.05))-.1,V(p.x-.9,p.y+.3-C(p.y+
.3,0,.6),p.z-.25).L()-.15));p.y-=.7;D pd=p.dot({0,-1,0});if(td<pd){c={.13,.54,
.13};R td;}auto f=[](D v){R Ab(fmod(v,1))>.5;};c=(f(p.x)^f(p.z))?V(.82,.15,.15):
V(.96,.63,.1);R pd;}V M(V e,V r,I b,I&h){V c,cc,n,l1=!V(0,-1,.3);for(I i=0,hh=0;
i<99;++i,h=1){D d=S(e,c),E=.01;if(d<E){n=!V(S(e+V(E,0,0),cc)-d,S(e+V(0,E,0),cc)-
d,S(e+V(0,0,E),cc)-d);if(b)M(e+n*E,n,0,hh);R hh?V():c*n.dot(l1);}e=e+r*d;}h=0;R{
.92,.95,.95};}I main(){I w=512,h=w,S=9;V T(.4,0,0),E(-.5,0,1.3),Z=!(T-E),X=!(Z*V
(0,1,0)),Y=!(Z*X);auto d=new char[w*h*3];for(I y=0,x,s,t;y<h;++y){for(x=0;x<w;++
x){V c;for(s=0;s<S;++s){D xt=(x+R1())/w*2-1,yt=(h-y+R1())/h*2-1;c=c+M(E,!(X*xt+Y
*yt+Z),1,t);}auto p=d+y*w*3+x*3;p[0]=Sq(c.x/S)*255;p[1]=Sq(c.y/S)*255;p[2]=Sq(c.
z/S)*255;}}printf("P6 %d %d 255\n",w,h);fwrite(d,1,w*h*3,stdout);delete[]d;R 0;}