Hitmontop in depth
The horn that serves as its axis
The Japanese name, カポエラー (Kapoerer), comes from capoeira, the Brazilian martial art built around spins, ginga and circular kicks. The whole design is there. The English name breaks the joke shared by its two brothers — Hitmonlee for Bruce Lee, Hitmonchan for Jackie Chan — and changes the reference from an actor into an object: hit, monster and top, the spinning top.
The horn on its head is made of the same material as its hair and claws, and keeps growing throughout its life. It is the point of support around which it rotates, and explains why the descriptions insist so much on centrifugal force.
A kick that was its own for six generations
Triple Kick, which it learns naturally from level 0, was its exclusive trademark for a long time: until Generation VII, no other Pokémon could learn it. It hits three times with increasing power, and each impact has to land for the next one to happen, making it an unreliable move, but also the perfect candidate for Technician, which boosts each hit separately.
That ability, precisely, was not there from the start: it arrived in Generation IV. Before then, it only had Intimidate, and its role was limited to switching in, lowering Attack and taking hits. With Technician, a whole bank of weak moves — Feint to lock down a turn, Bullet Punch or Mach Punch to finish something before it can respond — became worth using. The obvious comparison is Scizor, which uses the same ability with 130 Attack instead of 95; the difference in raw power explains why one is a regular in the higher tiers and the other is not.
Three endings for the same egg
What makes this line unusual is not the Pokémon, but the mechanism. Tyrogue spreads 210 base points across six identical blocks of 35 and, upon reaching level 20, checks two of them to decide what it becomes. Attack higher than Defense gives Hitmonlee, with 120 Attack and 53 Defense that falls apart to almost anything. Defense higher than Attack gives Hitmonchan, with 105 and 79. An exact tie gives Hitmontop, the only one of the three with equal figures, 95 and 95, and the only one that does not specialise. All three share the same 50 HP, the same 35 Special Attack and the same 110 Special Defense.
In Gold, Silver and Crystal, the only way to obtain any of them was the Tyrogue given by the Karate King in Dark Cave, in Johto, so the branch choice was decided entirely through training before level 20. In Crystal, Kiyo is also a named character with his own battle.
Where it is worth taking it
In a normal playthrough, its time is the middle stretch: Intimidate lets it endure switch-ins against Normal-, Rock- or Dark-type trainers, and with Dig at level 32 and Close Combat at 36 it has enough coverage for the final stretch without relying on TMs. Rapid Spin, at 16, clears Spikes and Stealth Rock if someone has set them.
What you should not do is try to use it as a pure attacker. With 70 Speed, it moves after almost everything that can hurt it, it has no way to recover health beyond Rest, and its two most common weaknesses — Psychic and Fairy — are spread throughout the modern Pokédex. Against a Flying type, it simply should not be on the field.