S - I just got home from Hockey and am wired and won't sleep for a few hours, so I'll help you out here. I did a fair share of bartending back on the east coast and we entertain quite a bit here and can offer some advice, and maybe help narrow down your list.
Whisky, Bourbon, Rye (same as Canadian Whisky, no?) - These are a guys drink mostly or older women. It depends on who you are entertaining. It's safe to have a good house rye on hand I'd recommend a bottle of CC, or some Crown if you want to splurge.
Gin (the tiny bottles don't count) - great with tonic or 7up. Also a nice base for Martinis if that's your thing. I'd say this would be a nice to have, but certainly not up there with Rum or Vodka
a good smooth Scotch - great if Granpa or IG are coming to visit. The younger Canadian crowd won't drink much of it, I wouldn't think. Make sure you like it before you spend $$$ on it, It's not cheap
Absinthe (mmm, green) - Am guessing you are referring to creme de menthe here??? Nice liqueur to throw into a blended drink I guess.
some of the common liqueurs such as brandy and sherry - Not sure I'd qualify these in the common category such as Kahlua, Baileys etc. Not needed.
varieties of Schnapps - substitue with vodka and a little flavored liqueur. You don't need 26's of pepermint shnapps hanging around...
Vermouth - only if you're making martinis obviously
Drambuie (I don't even know what that one is, actually) - it's a sweet whiskey type liqueur with honey.
Sambuca, Ouzo, Everclear, Tequila, - shooter stuff. If your party gets out of control this comes in handy. I don't stock any of it
Blue Curacao (that shit's in everything!) - A must have for me, since I make a personalized version of Blue Hawaii's all summer long
Obviously your Vodka and Rums are the most important since they give you the most versatility and are always the most popular. Don't forget the daquari mix and grenadine... those are essentials for summer foo foo's