__washucall:
Any cases of undefined behaviour causes mocking compiler diagnostics, sometimes including links to The Quiz.

__lspirocall:
Downloads L. Spiro Engine and calls the named function found there.

__fastcall22:
Slightly faster than __fastcall21, but not quite as fast as __fastcall23

__sicranecall:
Optimised for obscure corner cases, probably containing at least one template and maybe some pointers to members

__tomslopercall:
Optimised for business logic.

__alvarocall:
Only mathematical types can be passed and returned.

__tomslopercall:
Optimised for business logic.

I have the feeling this would be a boon on enterprise.

__alvarocall:
Only mathematical types can be passed and returned.

But wait, isn't that what C has always been doing? =/ (pointers are numbers after all)

But wait, isn't that what C has always been doing? =/ (pointers are numbers after all)

<pedanticmode>pointers aren't integral types and in fact need not even have a total order</pedanticmode> (that said I have used __alvarocall every now and then and would definitely recommend it whenever you are writing numeric algorithms as the alvarofloat does provide a bit more precision than its standard counterpart)

__hplus0603call:
Parameters and return types must be POD. Implementation may be on a remote server, an appropriate protocol is synthesised and used depending on the amount of data.

__servantofthelordcall:
Elementary runtime errors are trapped and a detailed and helpful error message is displayed, with code examples of correct usage.

// Generally return nothing, but occasionally outputs messages for no particular reason
__lennylencall

// Occasionally causes a rhino to crash through your wall and debug your program for you.
__myopiccall

// Makes your program display cat pictures, and your soundcard play mewing noises.
__mittenscall

__kryotechcall

Behaves like Cryengine, but isn't quite Cryengine...