What types of alcohol will make meat tender when marinating?
Alcohol does not make the meat tender.  It even prevents the outside surface of the meat to fully absorb the flavours.  Then again, most marinades don't penetrate into the meat anyway.

When it comes to Shashlik, I think what is working for your uncle, is the time the meat spends in the fridge getting aged (they probably marinate for a day or more) and the enzymes break down the meat.

It is a myth that Alcohol or Acid make the meat tender.  In fact, they have the opposite effect.  Per food author Harold McGee's quote:


  Alcohol does denature and dehydrate meat and fish tissue, and the
  stronger the alcohol, the stronger this effect.


What you should do instead, is to cook off the alcohol from your marinade first. The ingredient that keeps the meat juicy is salt which most marinades have.

The less acidic marinade (beer versus wine) the more tender the meat.  However, some not so acidic wines end up flavouring the surface of the meat enough to provide a pleasant byte.