Alright; so taking a closer look at Dragonite tells us a few things.
- it is weak to rock
- it is x4 weak to ice
- it is weak to dragon
This immediately draws my attention to a
steel type, as steel resists all three of these attacks and is also SE against two of them. Let us take a closer look at possible participants:
Ferrothorn
Ferrothorn can fit on the majority of teams due to it simply being an amazing pokemon. Sadly, it doesn't resist ice due to its grass/steel dual typing, although this may not be a problem because many ice attacks are non-STAB due to the lack of ice type pokemon in OU. Taking a HP ice won't really bother Ferrothorn too much, it has pretty amazing special defense. It resists electric as well - in fact, between Dragonite and Ferrothorn, there are only ghost and ice that go unresisted. Rarely does a pokemon carry one move, so pokemon with strong dual-type attacks become problematic. Weavile is a great example; it has physical ice STAB and grossly outspeeds Dragonite even after +1; it may also carry priority ice shard. Ferrothorn isn't a great switch-in however due to low kick, which is a clean 2HKO (or OHKO if Weavile SDs on the turn). With free turns it can thunder wave, toxic, leech seed, spike or stealth rock.
Forretress
Who doesn't love Forretress (minus gen 3 players who have to deal with it every single battle)? Forretress is much more resilient to physical damage and isn't weak to fighting. As a bonus it can rapid spin, which may prove to be worthwhile due to Dragonite's ability Multiscale. It doesn't resist rock, but has such incredible physical bulk that it won't mind taking stone edge or even fighting moves. Aforementioned Weavile doesn't even 5HKO with low kick and CB Terrakion can't even 2HKO with Stone Edge after stealth rock. It can Volt Switch on incoming ghosts (particularly Jellicent) and go straight back to Dragonite or an appropriate counter/pursuiter. With free turns it can spike, t-spike, stealth rock, rapid spin or volt switch for momentum.
Bronzong
I know what you are thinking, but bare with me for a moment. Bronzong, much like Forretress, is neutral to fighting and has the added bonus of being immune to ground (or neutral to fire if you go for heatproof), taking little to no damage from EdgeQuake. It is also the only viable pokemon to learn a somewhat reliable sleep inducing move in Hypnosis
and stealth rock. It is also a solid check to Gliscor, who can just set up with taunt on both Ferrothorn and Forretress. It resists flying to boot; something Dragonite doesn't resist (and neither do Ferro or Forre)... although uncommon, certain Hurricane abuser could really hurt either of the aforementioned pokemons. Choosing Bronzong over Jirachi means you really want that levitate and/or hypnosis.
Scizor
Look, it's Scizor! We all know what Scizor does. A more offensively oriented partner to Dragonite unlike the previous candidates. Sporting priority + technician + STAB bullet punch and STAB U-turn off a monstrous attack stat, Scizor is pretty good at hurting things - and it learns pursuit too! Awesome, that'll teach that ice beaming Starmie. Scizor's bulk is somewhat lacking, but as previously mentioned it is a more offensively oriented partner for Dragonite.
Heatran
One of the better pokemon from DPP and also a steel type is Heatran. Flash fire is a great ability and it has extremely high special bulk. It has a wide variety of moves to its disposal and is immune to both toxic and will-o-wisp (while being able to pack both moves). Lava plume - the fiery equivalent of scald - is a great move. It can also set up stealth rock and check many troublesome sun-team pokemon. It is very weak to Dugtrio however. Sub/protect/torment/lava plume sets are hilarious.
Jirachi
Stealth rock? Check. Thunder wave? Check. Can be either physical or special? Check. U-turn and/or volt switch? Check. Hax? Double-check. Jirachi is great; sub/cm is beyond annoying and body slam (or t-wave) + iron head is extremely debilitating. Jirachi has less support options compared to aforementioned defensive pokemons though and is also less of a threat compared to Scizor. It's more of a middle-ground support'ish pokemon in most cases, although CM offensive sets are not unheard of.
Skarmory
If you have played gen 3, this big metal bird has almost certainly had vigorous intercourse with your mother at least once. Kind of like Bronzong but with no Hypnosis, rock resist or special defense. Does this mean Bronzong is better? Not quite, because Skarmory learns phazing, a reliable recovery move, spikes and has a nice offensive option in brave bird. It can also use taunt to win against opposing Forretresses and Ferrothorns.
Just some ideas, not really nominating anything yet. Will post my nomination later.