Genji:

His: Amour
Yours: beautiful

Jesse Mcree:
His: Handsome
Yours: Darling or Darlin

Hanzo:
His: honey
Yours: Gorgeous

John Morrison:
His: Commander
Yours: Lieutenant

Widowmaker:
Hers: Amelie ( she doesn't like pet names)
Yours: Mon Amour ( she slips up occasionally)

Tracer:
Hers: Sweetheart
Yours: Love

Mercy:
Hers: Angel
Yours: Liebe ( it may be German but Switzerland doesn't have their own language German was one of their many)

Reaper:
His: Sunshine( just to piss him off)
Yours: Y/n ( like Ameilie he doesn't like pet names)