Hitmontop

While spinning upside-down like a top, it fights opponents and kicking them.  The centrifugal force boosts all of the power of Hitmontop's attacks.  If you become mesmerized by its elegant dance-like kicks, you might be "drilled" hard if you don't make way for it.
Hitmonlee is focused on kicking.  Hitmonchan is focused on punching.  Hitmontop is focused on- whatever that fighting-while-spinning thing is.  It has low HP, just like any "Hitmon" does.  It has low Sp. Attack stats, but who cares?  It has tons of Physical moves.  It has okay Attack, Defense, and Speed stats.  But it seems to be really focused on Sp. Defense.  It's not too bad, but I think they could've equipped Hitmontop with some higher stats.
It can use Rapid Spin, which is good to use if your opponents use Entry Hazards, like Spikes, Stealth Rock, and Toxic Spikes, as well as moves like Bind.  It also has other useful moves.  For example, there's some of its great STAB moves, like Close Combat, Counter, Revenge, and Rolling Kick.
Hitmontop has some nifty abilities.  It has Intimidate, which lowers the Attack stat of the opponent's Pokemon that's in battle when Hitmontop is sent out.  It's not awful, but I'd stick with Hitmontop's other ability, Technician.  A really popular ability, Technician increases the power of moves with a base power of 60 or lower.  It's just incredible.
So Hitmontop is a Pokemon that isn't exactly the greatest, but has some up sides, and can be useful in the right hands.