For me, even though I haven't played it, the idea of a Drow Shadow Sorcerer 6/Hexblade Bladelock 14 is pretty enticing.

For one, it's a pretty solid gish, able to do pretty well in the frontlines with decent armor, your main stat for attack rolls and twice that for damage rolls (depending on how you roll Hex Warrior and Lifedrinker), access to melee cantrips such as Booming Blade and Greenflame Blade and short-rest slots for key spells such as Shield and Armor of Agathys, while still being a formidable caster with a variety of ranged cantrips (Frostbite, Fire Bolt, Lightning Lure, and of course Eldritch Blast) and a solid amount of crowd control spells (with the most notable exception of Evard's Black Tentacles, but that's that). However, the reason I like it is because it can act as a pet class as well; with the 6th level subclass features of both classes, I can have a Hound of Ill Omen running around with a Specter ready to contribute to the team, even if their power dwindles as you progress.

Not a Coffeelock, but it has quite the variety of tricks to its disposal. If you add the new spells and invocations from the UA, you could have it wear Heavy Armor without difficulties, while still wielding a Greatsword (which, thanks to the combination of Hex Warrior and Pact of the Blade, you can bypass the two-handed requirement and deal very solid damage), and with virtually no chance of losing concentration spells (since Sorcerers start with proficiency in Constitution saves, plus one of the ASIs will be sacrificed for War Caster, so that I can use Booming Blade or Lightning Lure as an OA). It's so chock-full of potential, solid early on (working well since 4th level, half of its main trick available since 7th) but always develops into something new and fun (with its main tricks fully developed at 12th, and maximum damage potential by 18th).

I also plan to have my next build probably be a Crown Paladin with either a Celestial or Hexblade dip. Celestial fits the theme (Scourge Aasimar + Crown Paladin) but has less synergy (several sources of healing, but still requires a high STR to function), whereas Hexblade is more optimal (Cha to attack and damage rolls) but contrasts with the theme. Either way allows for Booming Blade as OA, a good ranged cantrip in Eldritch Blast, short-rest smites at their lowest power (kinda like the UA application of Channel Divinity) and major crowd control (between War Caster + Booming Blade for the main event, Champion's Challenge CD, Spirit Guardians as an Oath spell and the Scourge Aasimar's nova mode, I can do quite a bit of damage while still exercising lockdown). Torn between either Sentinel and Tunnel Fighter (which is just an absurd combination alongside Spirit Guardians) or Dueling and Polearm Master (planning on using a Spear and Shield), though I may incline for the latter.

Regarding dips and dunks: a dip is a multiclass, no matter how deep it is. It replaces some class features for others, particularly in the intent of flavor or mechanical synergy. It uses the multiclass rules in its entirety (as in, you need to qualify by having the right ability scores) and is a deviation, albeit minor, of your class progression. Thus, it's fair to mention them as favorites, particularly if they help on a mechanical build, impart to the flavor, or both. After all, it's hard to determine where the dip ends and you effectively "dunk" into the other class; some may say that a dip is just 1 or 2 levels, since you don't sacrifice much (at best, your last ASI and/or your capstone) and most classes have their defining subclasses by 3rd level, while there's an argument that 3 levels could still be considered a dip (after all, most classes get their 9th level spells at 17th level, giving you 3 levels to play with). Yet, regardless of where the "dip" ends and a proper "dunk" begins, the fact that you'll usually still refer to the class with most levels as your "main" class still applies. Case in point: the first build I mentioned is primarily a Warlock with some Sorcerer skills, but it has 6 levels in Sorcerer, so it's a dunk by any means; however, I define it as a gish rather than a caster, and that's mostly because of its focus (most of its invocations are spent to boost melee damage, after all). A Life Cleric 1-2/Shepherd Druid 17-18 is primarily defined as a healer more than anything; Disciple of Life only requires the most minimal dip, you want to use your Cleric spells to buff, your Spirit Totem as Unicorn to take advantage of the heals, and getting Channel Divinity for Preserve Life is enough to merit getting a second level and sacrificing your ASI. Builds are best defined by function (primary and secondaries) rather than by class, since Paladins don't get Charisma to attack and damage rolls as a class feature or even subclass feature, and the only way to get that is by multiclassing - thus, a Paladin that dips even one level in Warlock for Hexblade features isn't a pure Paladin, but one probably dabbling in dark forces to gain more power, or a victim of circumstances, or perhaps even someone who's pragmatic and is willing to accept a gift without looking at who gives it.

I'd say the only reason why they shouldn't be mentioned, and that's playing for the other team, is that they're too ubiquitous - that is, since a lot of people are aware of them in these forums and understand what you get from them, counting them as "favorites" is unfair to those builds that use unusual dips or flavorful dunks. Even then, you can really ramp up the flavor by playing to their contrasts, and developing a story behind those; it's not the same to have a Paladin for all 20 levels played as an exemplar of its Oath, than a Paladin that taps into the power of dark weapons and reinforces its fighting skills, at the expense of the corruption it implies. They're two different visions, each of which can be seen through multiple lenses.

So, in short: dips that happen to be practical don't have to be boring, and hence can be favorites of people.