Fan Rotom is next. Lauded as the joke among the Rotom Forms, Rotom Fan actually has a bit going for it. As noted on Zapdos' review, the Electric Flying combination is fantastic defensively and offensively, and Rotom Fan can definitely abuse it defensively. Rotom has a generally good moveset that all of the forms can abuse and Rotom Fan is no exception.
So what is wrong with Rotom-Fan? Well, it has the same ability as all the other Rotom Forms. Levitate. The ability that grants most of the same benefits as being a Flying Type. Which Rotom-Fan is. So yeah, a normally great ability, utterly useless. Air Slash, while being the most accurate of the unique Rotom-Form moves, is far weaker than the rest (as Air Slash was the strongest Special Flying move aside from Aeroblast when Rotom-Fan was made) , and Rotom does not get any other Flying moves to abuse its secondary STAB with (and as Zapdos can attest, access to STAB Hurricane is a nice boon). Additionally, not having access to Roost also makes Rotom-Fan's bulk begin to pale in comparison to Zapdos as the lack of reliable recovery hurts a lot.
Annoying Fan
Rotom-Fan
Ability: Levitate
Item: Kings Rock/Leftovers
-Air Slash
-Thunderwave
-Confuse Ray
-Volt Switch
Nature: Timid (+SPE, -ATK)
EVs: 4 HP/ 252 SATK/ 252 SPE
This set is meant to abuse Air Slash and make Rotom-Fan as annoying as possible as a Togekiss-lite. Air Slash has a nice 33% chance to Flinch and is STAB, being the work horse of this set. Thunderwave provides team support, enables Rotom-Fan to outspeed many more targets and provides a 25% chance to not act. Confuse Ray further decreases the likelihood of the opponent attack by providing another 33% chance of not attack. So with Air Slash and Paralysis, that is about a 49.75% chance the opponent won't be able to move. Add in Confusion, and your opponent only has a 1/3 chance to move. Volt Switch is secondary STAB and allows Rotom Fan to pivot around and more easily spread Paralysis.
Kings Rock is for more Flinch chance, Leftovers gives Rotom-Fan more longevity over longer battles. Nature and EVs are to maximize damage and speed, so Rotom-Fan can outspeed as many targets as possible.