If your dad tends to his home bar as if it were his livelihood, then it's hard to go wrong gifting a nice bottle of booze. It's thoughtful, not too expensive or too cheap, and — unlike a new gadget or a DVD — it's not a problem if he already has one.
Maybe I'm biased: since my dad and I share a love for cocktails, I find myself often shopping for top-shelf spirits that aren't superpricey but also aren't run of the mill. Based on years of research, here are my recommendations for all types of drinking dads. Of course, I'm always looking for new booze to try, so add your own gift ideas in the comments.
For the Old-Fashioned Fan
If your dad is a bourbon drinker and you have money to burn, then you can find plenty of bottles priced as high as $100. (Perhaps Papa would appreciate Pappy Von Winkle?) But if he's fond of old-fashioned and manhattan cocktails, then I'd recommend one of my favorite affordable bourbons, Eagle Rare 10-Year-Old Bourbon  ($28, originally $30), which tastes far richer than its price but also mixes well.
For the Martini Drinker
If your dad is a vodka martini man, then chances are he probably already has a few bottles of Belvedere and Grey Goose hanging around. For a more unexpected but just as smooth choice, gift him a bottle of Hangar One  ($31, originally $37), distilled from wheat with a base of Viognier wine.
For the Cocktail Adventurer
If your dad is the type to try new cocktails, then give him a taste of pisco, the Peruvian brandy that's finding its way into an increasingly versatile menu of cocktails beyond pisco sours and pisco punch. The understated Barsol Pisco  ($26) will suit a cocktail adventurer's refined palate and taste for adventure.
For the Slow Sipper
If your dad likes his whiskey neat or on the rocks, then expand his learnings with a bottle of Redbreast 12 Single Pot Still Irish Whiskey ($65, originally $77) . It's aged like single-malt scotch, but the slightly earthy and carmel-y flavor leans more toward bourbon.
For the Enthusiastic Eater
If your dad loves food even more than mixology, then he's probably inclined to lean back in his chair with a drink after savoring a long meal. Introduce him to the Italian digestivo amaro, an after-dinner liqueur that's bitter yet herbaceous and a molasses-y liqueur. I particularly enjoy Averna Amaro Liqueur  ($25, originally $32), which is a well-rounded bottle to start with.
For the Serious Shaker
If your dad is really into mixology, then he can never have too many bottles of bitters. It's amazing how a few drops of a flavor-infused bitters can transform a cocktail into something new and different. Give him room to play around with this Fee Brothers Starter Set  ($46), a set of six versatile bitters from an exceptional brand.
For the Man of Leisure
There are certainly more expensive rums for sippin', and perhaps your dad would rather savor some Appleton Estate Extra 12-Year-Old Jamaican Rum  ($35, originally $43) on the rocks. But if he's a cocktail guy, then he's going to want a rum that's great for mixing. You can't go wrong with Bermuda's Gosling's Black Seal Rum  ($23, originally $27), perfect for a dark and stormy night.
Source: Flickr user Kate Anthony 
For the Sophisticated Silver Fox
Silver gin for the silver fox? If your dad likes his martinis dry and his shirts starched, then Nolet's Dry Gin  ($45, originally $53) is a must-try. I've been using this incredibly versatile, manly-looking gin in all sorts of cocktails lately, and it's fresh and fragrant yet also subtle.