Simón

(See-Mahn)

Yes 

Simon has little if anything to say in D.F. 

Instead, ¡Simón! is an amusing and emphatic yes!

With the proper accent, Simón garnishes an otherwise flat yes, with a sense of pride in admitting to something.

Me dijeron que tu eres el mero mero de por aquí.   ¡Simón! (People say you'e the man around here. You betcha sweet!)

Stretching the last syllable with a hint of disbelief reverses the meaning.

Feel free to become and instant chilango by  trading a dull Si! for a hearfelt ¡Simón! 

Equivalent expressions include: Cincho, is, is-barniz, ei (a).

Any of the above can be substituted by a subtle short whistle synchronized with a tilting of one's face, blink and a downward motion of the right hand coming  down emulating the pull of a string by the index and thumb.