Hmm, Azery and Hukuna justified their choices, must do the same cuz I like writting about the stuff I like (in this case, types xD)
1) Ghost - This is best type. Like, every day of the week, every month of the year, every gen of the franchise (except 1), ghost rules. One ghost to rule them all, one ghost to find them. Since I discovered pokémon had types and that there was this one type called Ghost, it's grown to be my undoubted favorite of all times.
Statistically and type-wise, I love them because no matter what type you pair ghost with, you'll get something awesome, making it the defacto most awesome type on existence. Immune to normal and fighting, resistant to bug and poison, weak to itself and dark, pretty much makes it so that no matter what secondary type you give a ghost, you'll always end up giving it more or at least an equal amount of resistances than it has weaknesses. And this is true, go look it up, EVERY type combo with ghost has either the same or more resistances than it has weaknesses, AND, there's only one type combo with quadruple weaknesses, ghost/psychic. All of this makes ghost one of the best defensive types in the game together with fairy, steel and poison in my book. But offensively, is also great, being the single best offender for neutral coverage in the whole game, paired with dragon: normal has ghost immune to it and is resisted by rock and steel; dark has nothing immune to it, but is resisted by itself, fairy and fighting; Ghost and Dragon, on the other hand, are each resisted solely by one other type (dark and steel, respectively) and have one thing immune to them (normal and fairy, respectively), making them the two best neutral offenders in the game.
Ghost also generally have great stats: they make up for generally low HP with great attack, defense, special attack, special defense and speed, and well, that in the cases where they actually have low HP. Even the two ghost types with the lowest BST, Shedinja and Sableye, are both beasts in their respective niches: if your opponent has nothing to hit Shedinja with you've won, as simple as that, and there are few things that can NOT get burned, poisoned, taunted, swaggered or shadow sneaked by a Sableye.
Move and role-wise, ghosts are defined by bulbapedia as "mainly used to inflict status conditions". Welp, not gonna say that's not true: most, if not all, of the ghosts I use have either w-o-w or toxic. But far from depending on those moves alone, ghosts can be good attackers, good defenders, good supporters, good whatever. They aren't the best at those roles (in general), but they can play every single one of them, being in my eyes as versatile as the normal type.
Ghosts are also annoying. VERY annoying. And that's another of the reasons that they're my fav type. Pain Split, w-o-w, destiny bond, grudge, shadow sneak, curse, hex, night shade, nightmare, trick-or-treat, cursed body, shadow tag.... they are the ultimate annoying type, and that strikes me in a good way. I love being able to annoy without having to necessarily stall to death the opponent, because that takes long and is boring.
Is a type that I can personally say I love each and every single pokémon on it design-wise. I have tried to find a ghost I don't like, and I can say there simply is none: from Shedinja to Giratina, all of them are great and lovable.
Most favorite ghosts: ALL OF THEM (top 1 being Gourgeist <3 )
Less favorite ghosts: none. If anything, there are some that are a pain to fight against (namely Cofagrigus, Aegislash, Trevenant), but that's part of their charm to be, so I can say no ghost type I don't like. Rotom forms I don't consider ghost types, because they're not.
2) Psychic - Had the best time of its life in gen 1, being immune to ghost and only having to worry about a strong STAB pin missile (this is, nothing at all XD), and despite further gens have only nerfed it with the additions of things like the dark type, instead of acting like the fanboys of dragon types do with fairies for being immune to their dragons, I instead love the dark type as well, so wicked cool of a type, but just not in my 3 favs (it actually takes the 5 spot lol). I will keep loving psychic and everything related to it, from the ability magic guard to some of my favorite moves, like psychic, miracle eye, trick room, and so on.
Not as notable type-wise as ghost is, but hey, you can only be so awesome. They instead have no immunities and just two resistances to fighting and itself (I always thought they should resist fairy and poison as well: such a high intelligence should be resistant against pixie magic and mundane chemical venoms), but a man can dream. Offensively, they're one out of 2 types able to handle poison super-effectively, and they can also hit fighting types pretty pretty hard.
They're very varied statistically as well. There are straight offenders like Alakazam, with gargantuan SpA and Speed, but horrible defensive prowess. Others, such as Reuniclus, can use magic guard and a variety of shenanigans such as trick room to last long. Some are bulkier or have tricks even dirtier than dark types, like Wobbuffet, so cheap that it will always wait for you to attack it first, and unless you have a status move or a SE move, if you switch into it, you've lost that mon. Oh, did I mention ghost types are immune to all trapping moves and abilities? another reason that justifies the spot they occupy for me xD
Most favorite psychics: all of them really, but Top spots are Reuniclus (is a CELL for arceus' sake), Delphox (favorite starter tied with Serperior), Sigilyph, Gardevoir and Malamar.
Less favorite psychics: the mega forms of mewtwo, overpowered as fuck and shouldn't exist in the first place, similar to mega metagross, and I guess I could count in mega gardevoir/gallade, but you can actually kill those, unlike the god-like fucks mentioned above. Hoopa-unbound would be here if A) it wasn't so sick-looking and it wasn't devastated by a single x-scissor.
3) Fairy - The type of hatred. Like really, reeeeally the type of hatred. A type fans complained, ranted, mistrusted, devaluated and hated upon learning of its existence, but if they had any reason (and they do in some things), the fault would ultimately be Gamefreak's, not the type. That's one of the things that makes it appealing to me: the fact that, just by existing, it can annoy and make mad so many people, is an incredibly cute and tiny beast that feeds on the hate it generates and only gets stronger and monster-like inside, and I tend to love characters like these in media. I still find it funny and ironic how the fairy type is basically the same as the dark type in gen 2 (both 1 immunity, fairy is strong against 3 and dark against 2, fairy is weak against 2 and dark is weak against 3), and yet everyone loved dark types and hated on fairy types. Must be because dark types didn't nerf dragons XD
But outside of the jokes, fairy is a very good type, at least to me, for two reasons: it gave poison a HUGE boost in the competitive scene, like, I never saw anything other than toxic before fairies, and I rarely saw poison types either, so it makes me such so happy that poison is made so worth by this type being weak to it. Unlike steel, whose offensive attacks suck outside of bullet punch/iron head/meteor mash/flash cannon (and why I think fairies didn't really helped steel that much), poison has always had the moves to become a good offensive type, but never had the chance as there were so many better choices to get rid of grass. But what you got for fairies? it seems to be you'll be needing good ol' poison for the pesky pixies. Derived from these, I love the fact that Dragalge gets used because it can get rid of fairies so well: Dragalge is a sick-looking dragon type, yet I bet my ass it would get less usage if fairy types weren't there to help it be SE against them.
The second reason is that it is a type built around special defense (in general, like how ghosts usually have low HP), and the majority are VERY good special walls, and have good movepools, derived from the fact that most fairy types were previously normal types, who have WIIIIIIDE movepools. Fairy clefable gets moves I'm sure it wouldn't if it was planned as a fairy type all along.
There are some things I'd change about fairies tho, is not all love and roses as it is with ghost. For example, I'd made them no longer resist bug. The poor bug types, my 4th favorite type, don't need another thing resisting them, AT ALL. I'd actually make bug reist fairy instead, it would be so incredible for some overlooked bug/poison types. Psychic types (and arguably, grass types) should also resist fairy in my opinion.
Most favorite fairies: most of them, but Top spots are Clefable, Azumarill and Sylveon.
Less favorite fairies: xerneas, because geomancy is just too OP (you're not supposed to get 2 quiver dances in one, that's not how balance works you!), mr mime (because I think it should have been left as pure psychic or if anything be psychic/normal) and Aromatisse/Spritzee, because they CLEARLY had a chance to make them fairy/flying, and make Aromatisse into a neat design based on a flamingo or even the obscure plague doctor, but no, they had to go with the cabarette stubby thing. Such a let down.