Going to a goy to get healed for sickness of sakana,is a tooth pain considered internal sakana,and various remedies brought in the Gemara 

Mila from a goy to a yid and getitng healed from a goy

Yidden being midwives for non Jews and visa versa,and what's considered a mumar

Many machlokes Reb Elazar and Reb Shmuel Narchmani including how long the sun stayed up for yeshoshua,and halachos about yichud of a woman with a goy

Reb shailus's understanding in Rev Eliezer that a para aduma can't be bought from a goy because of vikchu and chshas rivia,and many questions in tanach on Reb Eliezer that we see they bought korbonos from goyim

More answers to the Stira if we can trust goyim with animals and does the Para aduma have a din kudshei mizbayach or mizbayach

21 questions on the three bchiyos of Rebbe

Partnerships with a goy and splitting the profits,and trusting a goy with animals in the punduk 

Machlokes Reb yosi and Reb Meir about selling and renting properties,bathhouses and fMikes's to goyim and cusim 

The issue of lo sichonem,not gazing at woman,and selling a goy different types of karaka al minas liktoz