[LukaAl]

  echo 'const int main[]={3850979413,184,3234285568,33554436,29869896,1207959552,1652109,3343384576,3522,1208291072,114887,3343385088,199,1208291072,1869376613,1919899424,169960556};'>t.c&&gcc t.c&&./a.out

But it is too long to tweet

[Edit]

Less compact but more readable:

  echo 'const int main[] = { 3850979413, 184, 3234285568, 33554436, 29869896, 1207959552, 1652109, 3343384576, 3522, 1208291072, 114887, 3343385088, 199, 1208291072, 1869376613, 1919899424, 169960556};' > test.c && gcc -Wall test.c -o test && ./test

[LukaAl]

Ok, now also the Mac version is twittable:

  echo 'const int main[]={1208,114434,2370306048,2101,834048,84869120,1818577091,1461743468,1684828783,10};'|cc -xc -ot -&&./t

The trick is to use retq instead of a sys call to exit and to strip some of the code that the compiler create when you call a function (pushq %rpb; moveq %rsp, %rbp; movl $0x0, eax;)