Name: Dewgong
New Stats: 100 / 70 / 110 / 100 / 120 / 90
New Typing: Water/Ice
Movepool Additions: Freeze Dry, Slack Off, Calm Mind, Hydro Pump
New Abilities: Hydration, Thick Fat, Swift Swim
Justification: Freeze Dry handles bulky waters, Slack Off provides reliable recovery, and Hydro Pump was added because Dewgong can't learn it for some reason. Swift Swim was added for flavor reasons.
Niche in OU: A Hydration user that doesn't have to rely on Rest for recovery. It's also the fastest relevant user of Swift Swim.
Example Sets
Name: Avalugg
New Stats: 115 / 137 / 200 / 44 / 66 / 28
New Typing: Ice/Steel
Movepool Additions: Heavy Slam, Icicle Crash, Magic Coat, Body Slam
New Abilities: Bulletproof, Filter, Sturdy
Justification: Avalugg's skin is as hard as steel, so a Steel-typing, Bulletproof, and Filter seemed like reasonable additions. Icicle Crash is a much more reliable STAB move than Avalanche, Heavy Slam and Body Slam make sense, due to Avalugg's massive weight, and Magic Coat protects Avalugg from status moves.
Niche in OU: A bulky Rapid Spinner for defensive teams
Example Sets
Name: Vanilluxe
New Stats: 71 / 105 / 90 / 130 / 95 / 99
New Typing: Ice
Movepool Additions: Spikes, Rapid Spin, Tri Attack, Focus Blast
New Abilities: Snow Warning, Water Absorb, Refrigerate
Justification: Snow Warning and Water Absorb are references to Vanilluxe's Pokedex entries, Tri Attack takes advantage of Vanilluxe's three parts and is boosted by Refrigerate, and Spikes and Rapid Spin are based on its conical shape. Focus Blast was added for competitive reasons, but it doesn't go against flavor.
Niche in OU: Thanks to Refrigerate, Vanilluxe's Rapid Spin is unblockable. Being the only viable user of Ice-type Weather Ball is also pretty nice.
Example Sets
Name: Beartic
New Stats: 100 / 145 / 95 / 80 / 95 / 75
New Typing: Ice/Fighting
Movepool Additions: Earthquake, Drain Punch, Knock Off, Ice Shard
New Abilities: Tough Claws, Thick Fat, Swift Swim
Justification: Tough Claws is a reference to its Pokedex entry, Thick Fat was added because, well, it's a polar bear, Knock Off provides strong neutral coverage, and Ice Shard provides STAB priority.
Niche in OU: Use Tough Claws and its sky-high attack to crush walls with its big, meaty claws
Example Sets