Golduck
Moveset Name: Physical Scarfduck
Move 1: Waterfall
Move 2: Zen Headbutt
Move 3: Cross Chop/Brick Break
Move 4: Ice Punch
Item: Choice Scarf
Ability: Cloud Nine
Nature(s): Adamant
EVs: 26 HP/252 attack/0/0/0/232 spe
This Golduck can work both as a lead and a late game sweeper. Golduck's attack stat is not that bad; it can utilize it well for a sweep, even with only a few options. The given EVs, when combined with a choice scarf, allow Golduck to hit 395 speed and outspeed all of the non-scarfed threats in UU except for Electrode. (correct me if I'm wrong)
Waterfall is for basic STAB. Zen Headbutt allows Golduck to hit the prominent fighting types in UU with a super effective hit. Ice Punch gives a super effective hit against Swellow, Altaria, and the grass types of UU. Cross Chop or Brick Break is up to preference of power versus accuracy and can hit Clefable (and Kecleon I guess) Super Effectively (I hate Clefable). Together, these moves cover almost all of the common leads in UU and many of the other pokemon in the tier. If I'm correct, you can get at least neutral damage on every pokemon in UU with correct prediction.
As for other options, there aren't many. Body Slam can be used if you really want to paralyze something, I suppose. If you want to use it in OU, give it 252 speed to tie with CS Heracross (if you want to risk that). One of the major reasons to use this in OU is that it can cripple Sandstorm Teams and Hail Teams with Cloud Nine.
Some problems that are unavoidable: Golduck has no physical options to take out bulky waters one on one, and certain physical walls are harder to take out with physical duck than special duck; however, some special walls are easier as well.
That's my first creative moveset.
If people show interest I'll add in some calcs tomorrow. Note that this is all in theory, I haven't been able to test it yet.