Additional Study Information: The purpose of this study is to test the effectiveness of cabozantinib with nivolumab and ipilimumab in rare genitourinary cancers that have no standard treatment options. Cancers include small cell carcinoma of the bladder; adenocarcinoma of the bladder; squamous cell carcinoma of the bladder; plasmacytoid urothelial carcinoma; any penile cancer; sarcomatoid renal cell carcinoma; sarcomatoid urothelial carcinoma; renal medullary carcinoma or other miscellaneous histologic variants of the urothelial carcinoma, such as, but not limited to micropapillary, giant cell, lipid-rich, clear cell and nested variants, large cell neuroendocrine carcinoma, lymphoepithelioma-like carcinoma and mixed patterns will be considered, as well as small cell neuroendocrine prostate cancer, testicular Sertoli or Leydig cell tumors, and papillary and chromophobe RCC.