Typing out of memory from what I remember without bothering to search,

- Small C

- RatC

- Borland Turbo C variants for MS-DOS, Windows 16 bit, Windows 32 bit, OS/2

- Borland Turbo C++ variants for MS-DOS, Windows 16 bit, Windows 32 bit, OS/2

- Borland C variants for MS-DOS, Windows 16 bit, Windows 32 bit, OS/2

- C++ variants for MS-DOS, Windows 16 bit, Windows 32 bit, OS/2

- Lattice C for MS-DOS and Amiga

- Watcom C and C++ for MS-DOS, Windows, OS/2, 16 and 32 bits

- Metaware C and C++ for MS-DOS

- Symantec C and C++ for Mac OS and Windows

- Metrowerks C and C++ for Mac OS, Newton, Epoch, Symbian and Windows

- Visual Age for C++ for Windows, Aix and OS/2

- Microsoft C for MS-DOS and Windows 16 bits

- Microsoft C/C++ 7.0 for MS-DOS and Windows 16 bits

- Visual C++ for Windows 32 and 64 bits, a brief support period for Mac OS as well

- LLC

- IBM Aix xlC

- HP-UX aC

- Solaris Sun Forte

- Intel ICC

- PGI C

- SN Systems C and C++ for Playstation

- Codeplay C and C++ for Playstation

- TI C

- ARM C

- Green Hills C

And many more I forgot to mention.