My ranking of the tastings I have attended (some once, others several times):
9. Beer-This is really the only tasting I would avoid. Speaking as a beer snob, there really isn't any beer on the ship that is better than mediocre, and drinking beers I got bored with 20 years ago is not my thing.
8. Whiskey-This one is usually held at 10:30 in the coffee shop, and you definitely need to like liquor if you are going. It is all glasses of straight whiskey. I happen to like whiskey/whisky and it's a reasonable priced and usually low key but friendly crowd. The pours are nothing special, usually an Irish, a Canadian, a bourbon, a blended scotch, and a single malt.
7. Cognac-Another late night, straight liquor offering. The problem is that the ship's Cognac selection is all from the mass market producers and I think this is the least variable tasting on the ship. You are going to get Hennessy VS, Remy Martin VSOP, usually Courvoisier VSOP, and an XO. Bonus points because one bartender used Hennessy XO as the last pour, and another let us all taste (as in, drops) the Remy Martin Louis XIII.
6. Rum/mojito tasting-Now getting into the range where the bartenders have some individual variability in what they serve, not my favorite as they usually offer straight white rum and/or cachaca among the options, which just isn't that pleasant to drink. No premium rums that I recall.
5. Mixology-A different experience every time and a favorite of many. Usually too many fruity/sweet/dessert cocktails for my personal preference, but always worth trying.
4. Tequila/margarita tasting-I have had quite different experiences at this one, some featuring more straight tequila and others concentrating on margaritas. Variability is always good. Bonus points because I like tequila but don't drink it that often.
3. Martini tasting-The only tasting I left walking on a slant. Unfortunately, for informative purposes something close to the original martini (a lousy cocktail with way too much vermouth) is usually served, but you will always get a nice dirty martini, usually a chocolate martini and 1-2 other fruity things.
2. Wine (many variants, e.g., New World, Old World, premium)-usually an experienced bartender who knows something about wine, and essentially a new experience every time.
1. Premium whiskey-Did this one last cruise. The first two offerings were uninspiring (Woodford Reserve and some Crown Royal 'premium' product), but the last two were Johnnie Walker Blue and Glenmorangie Signet, so this wins easily.
Not yet tried: Champagne (July 2019!), chocolate and liquor (we have a type I diabetic in our usual group, so tend to avoid candy)