TinyCC (aka TCC) is a small but hyper fast C compiler. Unlike other C compilers, it is meant to be self-sufficient: you do not need an external assembler or linker because TCC does that for you.
TCC compiles so fast that even for big projects Makefiles may not be necessary.
TCC not only supports ANSI C, but also most of the new ISO C99 standard and many GNUC extensions.
TCC can also be used to make C scripts, i.e. pieces of C source that you run as a Perl or Python script. Compilation is so fast that your script will be as fast as if it was an executable.
TCC can also automatically generate memory and bound checks while allowing all C pointers operations. TCC can do these checks even if non patched libraries are used.
With libtcc, you can use TCC as a backend for dynamic code generation.