it gained its fame in vgc2010, the year where all the ubers were allowed in. the most prominent was kyogre. scarf kyogre's water spout was a little much to handle, so people looked for creative ways to handle it and in came hitmontop. with access to fake out, wide guard, helping hand, and feint, hitmontop made the perfect partner for kyogre in helping it do more damage or preventing enemy kyogres from steamrolling. in the beginning of vgc2010 the hitmontops were slow, but by the end everyone was pretty much running max speed hitmontop in order to try to beat other hitmontops. this deadly combo was dubbed topogre.
in bw doubles/vgc2012 hitmontop pretty much did the same thing. it usually would be packing a fighting gem so that its close combat would do big damage. this time instead of partnering with the now banned kyogre, it was partnered with volcarona. topmoth worked because hitmontop could generate free turns through fake out and wide guard protection (from rock slide) so that volcarona could quiver dance up and sweep.
in xy doubles/oras doubles/vgc2014 hitmontop is dead bc its a shit mon and everything resists its hits and talonflame and will o wisp mega gengar and defiant bisharp getting stronger (mega gengar will o wisps top, traps it, and the game becomes a 1v2 because a burnt hitmontop does no damage)
sets i like are:
dpp: fake out, wide guard, helping hand, feint (close combat is an option but i like full support)
bw: fake out, wide guard, close combat, helping hand
xy/oras: fake out, wide guard, close combat, feint/helping hand
latios has always been an issue for hitmontops throughout the generations.
nowadays: talon, mega gengar, mega metagross, mega diancie (diansy in smogon doubles)
good article on top:
http://nuggetbridge.com/articles/history-lesson-hitmontop-and-why-you-use-it-now/