I'm disappointed Surskit is not listed in the OP.
It is obviously quite different from its evo, and STAB Hydro Pump in the rain + Swift Swim makes it a formidable opponent for many teams not prepared to face it. Its unique typing also offers resistance to the infamous ground + ice combination, a feat no other Pokemon can boast with typing alone. In fact, a good use of Surskit would be to use Shed Shell Registeel to set up rain as Dugtrio comes in. You can switch to Surskit as it EQs you, which, thanks to Surskit's amazing typing and decent 32 base defense, will only manage 81.4% - 96.4% on you with Life Orb. You can then LO Hydro Pump it for 292.5% - 345.3%, instantly killing the motherf-
Anyway.
I'm thinking about testing BUpassing with Floatzel to DDnair. Dragonair resists both of Floatzel's weaknesses and the defense boost would help Dragonair take Sceptile's Leaf Blade and random Aqua Jets. 1 BU + 1 DD lets Dragonair wreak havoc on a large portion of the metagame. The problem, of course lies in that both Floatzel and Dragonair are horrendously frail, and that Floatzel's counters generally shat on Dragonair as well (bulky waters/grasses), so it may not pull off that crucial Dragon Dance :(
If it does though, though:
+2 LO Jolly Dragonair Outrage vs max/max+ Venusaur: 84.1% - 99.2%
+2 LO Jolly Dragonair Outrage vs max/max+ Milotic: 80.2% - 94.7%
+1 LO Jolly Dragonair Outrage vs 120/152 Arcanine: 97.4% - 114.8%
+2 LO Jolly Dragonair Extremespeed vs 0/0 Sceptile: 94.7% - 111.7%
+2 LO Jolly Dragonair Extremespeed vs 0/0 Ambipom: 81.4% - 95.9%
+2 LO Jolly Dragonair Extremespeed vs 0/0 Ambipom: 57.9% - 68.4%
Obviously, you still need stuff like Registeel and Ice Sharders out of the way. Oh, and Surskit in the rain completely counters Dragonair with Ice Beam too :(
I doubt it'll work, since they both have the bulkiness of wet cardboard, but it looks okay on paper... Any thoughts?