Exeggutor is one of the most common and useful Pokemon in RBY OU. While not omnipresent like Tauros, Snorlax, and Chansey, it is still an excellent addition to most OU teams. Exeggutor is easy to fit onto a team thanks to its ability to effectively fulfill many important roles. With access to Sleep Powder, Exeggutor is by far the most common sleeper in the game, and is often used as a lead. Its unique typing grants it useful resistances to Psychic and Earthquake. Exeggutor is also bulky enough to make good use of these resistances. For this reason, Exeggutor effectively deals with Golem and Rhydon, and is able to take a few Psychics from the likes of Alakazam and opposing Exeggutor. In addition, a healthy Exeggutor also works as a decent answer to Snorlax and Tauros, especially if you can switch into them as they use Earthquake. While limited, Exeggutor's offenses should not be underestimated either; Exeggutor's Psychic gets STAB and comes off a 348 Special stat, and Explosion can KO Chansey or a Psychic-type trying to tank Psychic.
Thanks to its bulk and useful resistances, Exeggutor is the most reliable sleeper in the game, as it will find many opportunities to switch in and put something to sleep via Sleep Powder. Exeggutor has the ability to take hits from many common Pokemon such as Alakazam, Exeggutor, Golem, Rhydon, and Gengar, and can easily switch into Earthquakes. Exeggutor can also switch into Chansey as it uses Softboiled or Thunderbolt. It can even afford to take Body Slams and non-STAB-boosted Ice-type moves in a pinch. However, Exeggutor is slower than the other two common sleepers, Jynx and Gengar, which means that they will be able to put Exeggutor to sleep before it has a chance to reciprocate. For this reason, if Exeggutor is the only Pokemon with a sleep move on your team, it's a good idea to switch to another Pokemon, such as Alakazam or Starmie, to take the sleep and save Exeggutor and its Sleep Powder for later. Psychic is Exeggutor's main attacking move, and hits any non-Psychic-type Pokemon, except for Chansey, very hard. Explosion is Exeggutor's best option against Chansey and Alakazam. It is also very useful against other defensive Pokemon, such as Starmie and opposing Exeggutor. Explosion can also work as an emergency stop to sweepers such as Tauros, Snorlax, Slowbro, and Zapdos. It is a key move in Exeggutor's moveset, as Exeggutor's role in most battles consists of spreading status, sponging physical attacks generally from Rhydon, Golem, or Snorlax, scaring them off with Psychic, and then Exploding on a wall or an offensive threat.
There are three main options for the last slot. Stun Spore is probably the most common of the three; it provides a secondary status move, allowing Exeggutor to cripple many of its common switch-ins such as Alakazam, Starmie, Jynx, Lapras, opposing Exeggutor, and even Chansey. It's also useful for the occasional match-up with Tauros during the late-game part of the battle. Double-Edge can be useful for common switch-ins with low Defense, such as Alakazam and Jynx, hitting them for around 40% damage. Double-Edge gives Exeggutor the chance to take out a paralyzed Alakazam switching into it without having to resort to Explosion, and might even be able to take out a low health Chansey as well. Double-Edge also hits opposing Exeggutor harder, but due to its recoil, and Psychic's chance to score a Special drop, this doesn't give Exeggutor much of an advantage over opposing Exeggutor. Mega Drain makes Exeggutor an even better counter to Rhydon and Golem. It is only a 3HKO on Starmie, so you will have to paralyze it first. Mega Drain's ability to regain HP also helps Exeggutor to stick around longer and potentially spread more status. Both attacking moves are good options against Slowbro, and help put it at low enough health to be KOed by Explosion.
Exeggutor is quite versatile for RBY, although it's advisable to stick to the standard set's moves. Exeggutor's multitude of resistances and its bulkiness allow it to use Rest effectively, especially when combined with paralysis support from other teammates. Hyper Beam is an offensive alternative to Double-Edge that can deal around 60% to Alakazam and Jynx and almost 50% to Chansey, being useful when they have been previously weakened. Leech Seed is not as useful as in newer generations, due to it only draining 1/16 HP, but the HP healed against Chansey is still significant. Leech Seed and Rest is a gimmicky combination but can sometimes work out, especially when your opponent is lacking in offensive options. Reflect is another defensive move in Exeggutor's movepool, as it helps it sponge hits from powerful physical attackers, such as Tauros and Snorlax. Reflect can also be used alongside Rest, but this strategy works better on Hypno due to its lack of a weakness to Ice-type moves. In general, the moves that scare Exeggutor out come from the special side, except for Zapdos's Drill Peck, so Reflect is generally a poor move on Exeggutor. Finally, Egg Bomb is a similar move to Double-Edge, but it is not recommended due to its low accuracy.
Checks and Counters
Exeggutor's counters can be arranged into two main groups: the three Recover users (Chansey, Alakazam, and Starmie), and other Pokemon that can hit Exeggutor hard with super effective moves, such as Jynx, Lapras, and Zapdos. However, note that none of these are sure-fire counters, as Exeggutor can put one to sleep with Sleep Powder, and use Explosion on another. It's a good idea to send one Pokemon in first to bait the sleep move to activate Sleep Clause. Good examples for this role are Alakazam, Starmie, Jynx, Exeggutor, and Gengar as long as you are careful to not switch into Psychic. However, keep in mind that letting your sleeper get put to sleep could mean that you won't be able to put anything to sleep in the future, unless you have another Pokemon able to induce said status. Alakazam and Chansey make great counters because they can easily shrug off any damage from Exeggutor's Psychic with Recover and Softboiled, respectively. Alakazam can also set up Reflect to avoid being OHKOed by Explosion, but should watch out for Double-Edge when switching in if it is paralyzed. Chansey is a riskier bet because it is generally more valuable than Alakazam, and you don't want to expose it to the threat of Explosion, but it can easily sponge Exeggutor's Psychic nonetheless. Starmie works similarly, and can outspeed Exeggutor and 3HKO it with Blizzard, but it hates paralysis and should also watch out for Mega Drain.
Jynx is probably the best Exeggutor counter, however. Jynx resists Exeggutor's Psychic and can scare it with a 2HKO thanks to its STAB Blizzard, and has the ability to outspeed Exeggutor and put it to sleep with Lovely Kiss in a lead match-up. Although it is 3HKOed by Double-Edge, Jynx works wonderfully against Exeggutor that lack a Normal-type move. Even against Double-Edge variants, Jynx can work as a good check if you predict properly. If Exeggutor takes out Jynx via Explosion, it is not all bad news, because that will prevent Exeggutor from Exploding on other Pokemon, such as Chansey or Alakazam, that are generally more useful than Jynx. Lapras is a great Exeggutor counter even though it doesn't resist Psychic; thanks to its great HP stat, Psychic is only a 4HKO. Articuno is a less common alternative to Lapras, but its STAB Blizzard is even more powerful. The other two legendary birds also work well against Exeggutor; Zapdos has a chance to 2HKO Exeggutor with Drill Peck, while Moltres's Fire Blast will always 2HKO it. Cloyster can also 2HKO Exeggutor with Blizzard, but takes over 40% from Psychic. If you have no better option, your own Exeggutor can also work as a check, being able to take many Psychics, wear it down with Psychic or Double-Edge, or threaten it with Explosion or a status move.
While Gengar, Golem, and Rhydon have no business taking on Exeggutor as they are countered by it, they are useful for switching into a predicted Explosion. However, because Exeggutor can hit them very hard with its other moves, doing this is very risky if you don't predict correctly. A low health or sleeping Pokemon can be a good alternative to those three for switching into an Exeggutor that might use Explosion.