More than two year later, after having consumed far more whisk(e)y, and being far more knowledgable, I have decided to update this with a somewhat more comprehensive answer. I'll leave my original answer below, but consider it outdated.
For american whiskey, the important ones that I believe are worth trying are:
- Buffalo Trace and related whiskeys. Buffalo trace is known for having a great product at an affordable price, and the distillery also owns and produces many fantastic whiskies including Pappy Van Winkle. It's worth trying the Pappy if you can find some for a reasonable price, but keep an eye out for Eagle Rare and George T. Stagg as well.
- Elijah Craig, a sweeter style of bourbon also at an affordable price, especially for a twelve year old bourbon. I get a bit of tropical fruit on the nose which leads into spiced, cooked fruit and creme brulee, with the fruit and spice lingering to the finish along with some cereal notes.
- Four Roses makes a decidedly more floral, drier style of bourbon than the previously mentioned ones and is also an excellent value. They also release small batch and single barrel expressions as well which are pricier but worth the splurge every once in a while.
- Moving on to rye whisky, I'd have to say Rittenhouse Rye is a must. Being a bonded whiskey, it's at a hefty 100 proof, but drinks remarkably well. It's great for sipping neat, on the rocks, or in cocktails.
- Old Overholt, despite being a "well" rye, is also fantastic. It lacks some complexity of some of the "better" ryes out there but for the price, it can't be beat and outclasses other whisky at a similar price point.
- Lastly, Angel's Envy has been putting out some fantastic bourbon and rye. This bourbon undergoes a second aging in casks used to previously age port, while the rye undergoes the same process in Caribbean rum casks. The finishing process adds a layer of complexity and flavor that you normally don't get in most whiskeys. They are a little on the pricey side ($50-80), but definitely worth trying. Angel's Envy is a bit of a young gun compared to these other brands but its late founder, Lincoln Henderson, was a legend in the bourbon world.
The above selection should be a pretty good start to getting familiar with American whiskey. Some other whiskies worth mentioning are Evan Williams, Woodford Reserve, and Blantons. There are plenty more good whiskeys out there, however there are just too many to name here!
Now! Let's go back to Scotch. I'll go with the format of my original answer and give break it down by region, but I'll give a little more description into each region and its whiskies this time.
Lowlands: There are not many distilleries in the lowlands, but the ones that are there tend to produce a style that is somewhat more lighter in style than other scotches. Auchentoshan in particular is notable for being triple distilled like many Irish whiskeys and comes in a number of varieties. The three wood is additionally notable for being aged in three types of barrels. In addition, the Glenkinchie malt is probably worth checking out from this region.
Highlands/Speyside: By far the most number of distilleries is located in this region. Speyside is a sub-region of the Highlands that the river Spey runs through and has the highest concentration of distilleries. Notable Highland/Speyside malts include:
- Macallan: The "original" Macallan line is aged exclusively in sherry casks and has been a favorite amongst both casual and professional whisky enthusiasts. Macallan also produces a "Fine Oak" line that is aged in both sherry casks and used bourbon barrels. It's ubiquitous in bars and archetypical of what a Speyside malt should be like.
- Glenmorangie produces a 10 year old malt aged in used bourbon barrels. While I find the original expression good, but somewhat uninteresting, the distillery is quite big in to experimenting with different finishes, aging the base spirit in a variety of different casks for two additional years. The Nectar d'Or is notable for having the whisky finished in casks previously used to age Sauternes, a dessert wine from France.
- Glenfarclas on the other end, makes whisky with an extremely pronounced sherry characteristic. If you enjoy sherry-cask aged whisky, this is a great one to try.
Other whiskies from this region that are worth checking out include the Balvenie Double Wood, Glendronach 15 year old "Revival", and Glenrothes Select Reserve.
Finally, we get to the coastal/island Scotch whiskies. These are notable for their use of peat when drying the barley malt during the scotch production process. Not all island whiskies are peated and not all mainland whiskies are unpeated however, so keep that in mind.
- From Orkney located off the tip in the northernmost part of Scotland, we have Highland Park, which is peated, but not heavily to give it a smokey flavor that is not too overpowering. The whisky is consistently rated as the top amongst professionals and for good reason. It's extremely well balanced and a great example of what scotch whisky can achieve when all the flavors work harmoniously together. It is also one of the malts used in the Famous Grouse blend.
- Oban and Springbank are both whiskies located along the coast of Scotland are good introductions to peated whiskies. They have a far lower level of peat in the product, giving just slight hints of smokiness.
- Talisker, located on the Isle of Skye has a similar peat level to Highland Park and is also a great example of a balanced, peated whisky.
There is one island in Scotland that is famous for its heavily peated, smokey whiskies, which is Islay, and large number of distilleries are located on it.
- The most famous Islay scotch is arguably Laphroaig, which is probably one of the most heavily peated whiskies in its regular expression. The only other regularly available scotch that reaches similar peat levels is the Ardbeg, also on Islay.
- Another popular, but extremely good scotch from Islay is the Lagavulin. Slightly less peat than the Laphroaig, it is the other established Islay scotch whisky. While the Laphroaig is decidedly more smokey, the Lagavulin has a bit more of medicinal notes to it and is also a consistent favorite amongst critics.
There's so many more out there that I could recommend such as the unique Bruichladdich line, which does an unpeated Islay malt, as well as the Caol Ila which has a good medium-high level of peat.
And of course, I haven't even gotten into international malts like Yamazaki from Japan, and Amrut from India. I suppose I'll have to revisit this answer sometime in the future.
The Macallan should be one of the first single malts someone should try if they are inexperienced in scotch, in my opinion. The Laphroaig, Arbeg, Caol Ila, and Lagavulin are great examples of smokier, peatier scotches, while something like the Yamazaki or Balvenie Doublewood are less pronounced in smoke flavors, and tend to exhibit more oak and maltier characteristics. The Glenrothes is a personal favorite as well. Depending on your preferences, any of these could be a favorite.
I guess I should elaborate a bit more, since my whisky knowledge has gone up since writing this original answer. It's good to try examples of whiskies from all regions so you get a representative taste.
Speyside: Macallen, Glenrothes
Islay: Lagavulin, Laphroaig
I'd say these give a solid overview of the different styles of scotch and are common enough that you'll usually be able to consistently order them at any place with a semi-decent scotch selection.