This thing has one of the best defensive typings in the game, and has the stats to back it up. Even if the opponent carries an Ferrothorn, who would seem to be the best at walling Jellicent, it will likely be burned by Will-O-Wisp. While its Defense stat is somewhat of a letdown, it more than makes up for it with its HP. It also has a great support movepool to abuse, including Will-O-Wisp, Taunt, and Trick Room. These traits make it one of the few Pokemon that can stand up to the might of Scizor. It isn't a slouch offensively either. It's one of the only viable Pokemon to have access to the incredibly powerful Water Spout, which can be a horrifying move to switch into when backed by a base 85 Special Attack and Choice Specs.
However, the major drawback to it is that it is not immune to entry hazards, particularly Toxic Spikes.
Abilities
Water Absorb: Usually the way to go. Allows you to recover as you switch in if you predict accordingly.
Cursed Body: Unreliable, but can be incredibly annoying when it works.
Damp: Stops Explosion. This is useless in single battles as Jellicent is already immune to it. It could find some use in doubles, but the nerf it received made it much less common, so stick to the other two abilities.
Stallbreaker
Item: Leftovers
Ability: Water Absorb
Nature: Bold
EVs: 248 HP / 216 Def / 44 Spe
- Scald / Surf
- Toxic / Will-O-Wisp
- Recover
- Taunt
Jellicent's speed might not seem appealing, it can actually work very well at being a stallbreaker, with access to Taunt, Recover, Will-O-Wisp, and Toxic. Scald works best with Toxic, as Scald has a good chance of burning the opponent anyway. Surf could be used for more power, but should only be used with Will-O-Wisp, as then, Jellicent will have to way to beat physical attackers that threaten it. Recover is crucial to the set, as it gives Jellicent much more longevity. Taunt can stop slower Pokemon on the stall team in their tracks, but Ferrothorn usually has to be burned first, as an uninvested Power Whip will 2HKO. 44 Speed EVs allows Jellicent to outspeed Choice Band Scizor and burn it, allowing it to take Pursuit with ease.
Specially Defensive
item: Leftovers
Ability: Water Absorb
Nature: Calm / Sassy
EVs: 252 HP / 36 Def / 220 SpD
- Scald
- Toxic / Will-O-Wisp
- Recover
- Shadow Ball / Ice Beam / Substitute
This set accomplishes what Jellicent does best: take hits and inflict status to stall. Scald is the choice of attacking on this set, as it has a 30% of burning the opponent. Toxic is preferred in the second slot, forming dual status options. Will-O-Wisp can be used over Toxic if you are paranoid about Ferrothorn, since Scald can be unreliable, and Ferrothorn is immune to Toxic. Recover gives Jellicent longevity. The last slot is open to a few options. Shadow Ball provides additional STAB, and can win stall wars with its Special Defense lowering effect. Ice Beam gets better coverage though. Substitute can also be viable, as Jellicent generally hates status.
Choice Specs
Item: Choice Specs
Ability: Water Absorb
Nature: Modest
EVs: 172 HP / 252 SpA / 84 Spe
- Water Spout
- Hydro Pump / Surf / Scald
- Shadow Ball
- Ice Beam / Energy Ball
This set attempts to lure in Jellicent's usual switch it, such as specially defensive Heatran, and kill them with the appropriate move. Jellicent is one of the few Pokemone to have access to the ridiculously powerful Water Spout, and will severely dent even those that resist it. Hydro Pump is preferred for when Jellicent gets lower on health, as it has high power. Surf is more consistent, and Scald has a burn chance, which gives Jellicent a bit of utility. Shadow Ball provides secondary STAB. The last slot has a few different options. Ice Beam is generally preferred, as it hits Dragonite, who can be problematic to this set. Energy Ball could also be used to hit Quagsire and Gastrodon hard.
Other Options
Giga Drain might seem tempting on the choice specs set over Energy Ball, as it can give Jellicent enough health to give it a high-powered Water Spout again, but when you realize that Tentacruel is a common switch-in to Jellicent, it can actually be dangerous, as Liquid Ooze will hurt Jellicent instead. Magic Coat is another support option, but Jellicent has a hard time fitting it onto a set. ResTalk could also be used, as Jellicent is often targeted by status. Hex could be used over Shadow Ball on the Specially Defensive set.
Counters
Celebi and Shaymin are probably the best counters out there, as they both have Natural Cure. Both must watch out for Ice Beam, and the former has to watch out for Shadow Ball. If Jellicent lacks Will-O-Wisp, Ferrothorn can check the Specially Defensive set, but has to be careful when taking a Scald. Specially Defensive Tentacruel walls the Choice Specs set, and can scares it away, or poisons it if it stays in.