Jynx can be obtained through an in-game trade with a man in Cerulean City. You will need to give him a Poliwhirl. Smoochum can only be obtained through breeding.
While Jynx may be the definition of a glass cannon with low defenses and a fantastic Special Attack stat, you may want to perform a hit-and-run strategy with her. She can be a great special sweeper, as she doesn't have many counters (Jynx gets excellent coverage with just her STABs alone), and although she might be hard to work with at first, she'll prove herself to be an absolute monster by the end of the game. However, using Jynx in a Nuzlocke would require an in-game trade, a feature many nuzlockers do not allow themselves to use. It can also prove slightly difficult to use if you have one, as well; though its typing gives it fantastic STAB coverage, it is also left with a multitude of weaknesses as well as very few resistances. It doesn’t help that Jynx dies to pretty much any strong physical attack, too. When used correctly, Jynx can be a complete sis that’ll sweep the entire Elite Four with little to no backup. When not used correctly, it’ll die to the first Rattata you run into.
Rival (Pokémon Tower): Jynx will make short work of Pidgeotto and Exeggcute, unless your rival chose Bulbasaur, in which case Jynx will still be able to destroy an Ivysaur. Keep her well away from his Growlithe for obvious reasons. Keep her away from Gyarados, which could potentially Thrash her to death, but a Shadow Ball or Ice Punch can make quick work of Kadabra.
Giovanni (Rocket Hideout, Ground-type): Ice Punch will easily get rid of Giovanni’s Onix and Rhyhorn, but Kangaskhan poses a huge risk of outright OHKOing with STAB Mega Punch off of 95 base Attack. If Jynx has to face off against it, use your special-based moves; Brick Break may seem tempting, as it’s super-effective, but keep in mind that 150 base power off of 50 base Attack onto 105/80/80 defenses really isn’t going to do anything. You’re better off just going with your STAB moves (Ice Punch, Ice Beam, or Psychic).
Gym #4 - Erika (Celadon City, Grass-type): Her Ice attacks will be very useful against the Grass types. There's not much you need to watch out for apart from status infliction and the powerful Acid which can really do damage due to Jynx’s piss-poor Defense stat.
Gym #5 - Koga (Fuchsia City, Poison-type): Target the low Special Defense of Koga’s Koffings and Weezings with STAB super-effective Psychic. If you don’t OHKO them, you should probably take a virtual hammer and smash the RNG over the head. Muk, however, is a completely different story. It has Special Defense and HP up the wazoo, as well as STAB Sludge coming off of a high Attack stat. Tread carefully around this thing, or it might just escape the OHKO with a sliver of health and retaliate with a OHKO crit Sludge.
Fighting Dojo (Saffron City, Fighting-type): Due to her strong Psychic attacks, Jynx will quickly make work of everything in here, but just hope you've got a fast one: any strong Fighting attack will quickly take her down. Keep her away from Hitmonlee, but she'll take out a Hitmonchan easily.
Rival (Silph Co.): Jynx will eat Pidgeot and Exeggcute for breakfast. Alakazam’s only attacking move is Future Sight, so you can allow it to die a slow and painful death. Gyarados and the starters will not be easy for Jynx to take down unless it's Venusaur. Growlithe is obviously still an issue, but STAB Psychic may have the ability to take it out.
Giovanni (Silph Co., Ground-type): About the same as the last fight with him. Speed forth with Ice Beam and Psychic, and remember to stay the hell away from Kangaskhan.
Gym #6 - Sabrina (Saffron City, Psychic-type): Jynx will resist Psychic attacks and can retaliate with moderately strong Ice-type STAB moves. However, just try to use a Physical Attacker here - Alakazam has laughable Defense.
Gym #7 - Blaine (Cinnabar Island, Fire-type): Keep Jynx well away from everything in here - her fantastic Ice STAB will be useless here and she'll be mincemeat after one Flamethrower or Fire Blast.
Gym #8 - Giovanni (Viridian City, Ground-type): Free experience, as literally all of Giovanni’s Pokémon are hit super-effectively by your STAB Ice Beam. Try to avoid Earthquake with Jynx, though, and maybe switch in to a Flier when you think it's coming.
Rival (Route 22, pre-Elite Four): Pidgeot and Rhyhorn are easily taken down with Ice Beams. Exeggcute will die easily. Alakazam and Gyarados you should leave for something else. Venusaur is vulnerable to both of your STABs, so pick whichever one’s stronger (hint: it’s Ice Beam). Jynx won't fare well against the other starters.
Elite Four Lorelei (Indigo Plateau, Ice-type): Jynx doesn’t do well here at all. Psychic on Cloyster is about all it can do, as everything else is either too bulky for Jynx to take down quickly, too dangerous for her to fight, or both.
Elite Four Bruno (Indigo Plateau, Fighting-type): Clean sweep. Ice Beam the Onixes, Psychic the Fighting-types. The only real concern you might have about this battle is whether Jynx is fast enough to outspeed and OHKO Hitmonlee before it can hit her with a powerful Brick Break or Mega Kick. But unless you have a Speed-lowering Nature, awful Speed IVs, and few to no Speed EVs, you should be fine.
Elite Four Agatha (Indigo Plateau, “Ghost”-type): Be careful. Shadow Ball and Shadow Punch will probably score a OHKO on Jynx, but you can one-shot everything Agatha has with Psychic, as all of her Pokémon are part Poison-type. Again, the main risk here is being outpaced, so if you’re not sure you have a higher Speed than Agatha’s Pokémon, Jynx should probably GTFO and make way for something a bit more durable.
Elite Four Lance (Indigo Plateau, Dragon-type): Do I even need to say it? Spam Ice Beam. Forever. Except against Gyarados, as its Hyper Beam can probably kill you. And Aerodactyl, since it has insane Speed and can nail you with AncientPower or Hyper Beam, both of which will undoubtedly OHKO you. But against the Dragonairs and Dragonite? Go to town with dat Ice Beam.
Champion Rival (Indigo Plateau): Arcanine/Charizard are no-nos. Pidgeot, Exeggutor, Venusaur, and Rhydon again all die to Ice Beam. Everything else is kind of shaky. You know the drill by now.
The moves you start out with depend on what level of Poliwhirl you trade for Jynx. Jynx’s starting moves are Pound, Lick, Lovely Kiss, and Powder Snow, in that order. They will have been deleted in that order to make room for new moves if you got your Jynx at anywhere above level 21, which is when it learns DoubleSlap. Of all of Jynx’s starting moves, Lovely Kiss is the best in the long term, while Powder Snow offers a nice, if quite weak, Ice-type STAB move for Jynx to run off of her stellar Special Attack stat. Pound and Lick both suck, but you should be getting rid of them soon enough. The aforementioned DoubleSlap is garbage, but if you really want to, you can use it over Pound. Honestly, though, Pound is probably better due to its better reliability. At level 25, Jynx will try to learn Ice Punch, which is absolutely fantastic, as due to the lack of the physical/special split in this generation, it will run off of Jynx’s vastly superior Special Attack. Mean Look comes at level 35, and due to it being extremely situational, it’s not really advisable for you to teach it to her. Fake Tears, which comes at level 41, can be interesting, but keep in mind that Jynx is normally powerful enough to OHKO or 2HKO anything in her path around this stage of the game, so it isn’t really necessary. Body Slam comes at level 51, and while it has a nice 30% paralysis rate, its lack of STAB and the fact that it comes off of Jynx’s very weak Attack stat will cause it to be not the greatest of options. It might be worth keeping around just for the paralysis chance, though, if you’re not running Lovely Kiss. Perish Song at level 57 can be useful for beating tough foes, but Jynx’s frailty makes it a crappy staller, so if you’re going to run Perish Song, switch to something else to stall out the turns. Finally, Blizzard comes at level 67, and while it may be more powerful than Ice Beam, its 70% accuracy as well as the fact that you probably won’t be at that level until you’ve beaten the Elite Four already make it a poor choice.
Calm Mind, Psychic, and Ice Beam are the trinity of TM moves that you should always teach Jynx. Ice Beam and Psychic are extremely powerful STABs, while Calm Mind boosts Jynx’s power while also making her bulkier on the special side. Water Pulse can be useful, but it provides slightly redundant coverage alongside Ice Beam (although it does allow Jynx to hit Fire-types). Blizzard is a workable option, but its accuracy makes it a bad move for a Nuzlocke. Just stick with Ice Beam. Hidden Power can be useful if you get a good type, but make sure it’s a special-based type, preferably Electric or Grass. Shadow Ball and Brick Break are both reasonable options to increase Jynx’s coverage, but they run off of Jynx’s pitiful Attack stat, meaning they won’t do too much damage, even when super-effective.
Tutor-wise, Substitute can work well with Calm Mind, whereas Dream Eater may pair well with Lovely Kiss.
Recommended moveset: Ice Beam, Psychic, Calm Mind, Lovely Kiss
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
What Nature do I want? Jynx will always have a mild nature from the trade, which is an incredible nature for her. She would prefer modest or timid, but it's far better than a bad nature.
How good is Jynx in a Nuzlocke? While often underused, Jynx is great in a Nuzlocke. She has excellent coverage and great Speed, as well as being able to sweep most foes. She has very few hard counters. Her movepool will serve you well against many of the game's strongest trainers, especially Lance, whose team is almost entirely weak to Ice.