MUST HAVES (IMHO):
Vodka
Ketel One - very good, from Holland
Gin
Tanqueray Ten
Single Malt Scotch Whiskey
Springbank Hazelburn 8 year old - hard to find, but it is Sssensational
Oban 14 year old - finishes with a hint of caramel
Irish Whiskey
Jameson Special Reserve 12 year old
Beer
Birra Moretti from Italy - Really beautiful lager and the label is legit
Red Wine
Louis Bernard Cotes du Rhone '07 (France) - widely available for under $10 a bottle and you get something from the '07 vintage which is the best in a few decades
Paul Autard Chateauneauf du Pape '07 (France) - Again, supposed to be a perfect vintage in this area of France - about $35 and blows away some $100 bottles
White Wine
Tramin Pinot Bianco '08 (Italy) - might be the best white for under $15 anywhere
La Cana Albarino '08 (Spain) - might be the second best white for under $14 anywhere
Bubbles
Dumont Brut (Champagne) - $30 and destroys Clicquot and many other better known chamgagnes
Nino Franco Rustico Prosecco (Italy) - $15 and will destroy many champagnes at $30-$50.
Vega Barcelona Brut Reserva (Spain) - Same as above, legit stuff
I know very little about tequila, rum, brandy, etc etc
Should also have a bottle of Sweet Vermouth and a bottle of Campari.
As you can see, I like to spend way more on liquor and spirits than I do on wine. There are thousands of incredible value wines out there that are as good as or better than $50, $75, $100 wines. Hope this helps