Here's a Pokemon that gained a fair amount of utility from Aegislash's removal.
Cofagrigus
Pokedex Number - 563
Type(s) - Ghost
Base Stats - 58 HP / 50 Atk / 145 Def / 95 SAtk / 105 SDef / 30 Spe
General Analysis of Pokemon/Current Roles in OU -
While Cofagrigus was rarely hinder by Aegislash itself, the removal of Aegislash has made Pokemon that Cofa checks and counters far more common as well as naturally increasing Cofa's Spin-Blocking viability. Thanks to the addition of Toxic Spikes to its egg moves in XY, Cofa is one of the 3 fully-evolved Ghost-types to have an entry hazard and one of the very few non-Poison-types to get the move. Mummy, Cofa's signature ability, nullifies foe's abilities on contact; reducing major threats like M-Medicham, M-Mawile, Azumarill, M-Pinsir, Scizor, and Talonflame to much more manageable levels. Cofa's typing allows it to entirely wall M-Heracross, Mummy renders M-Pinsir
completely unable to touch Cofagrigus after it activates, M-Medicham arguably struggles more against Cofa than it did Aegislash with no way of hitting Cofa Super Effectively, and Cofa can threaten each with a WoW burn.
Potential Movesets:
Utility
Cofagrigus @ Leftovers
Ability: Mummy
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Will-O-Wisp
- Shadow Ball
- Toxic Spikes / Pain Split
- Haze
This set does a little bit of everything; it blocks Rapid Spin, spreads burns, sets up hazards, removes the boosts accumulated by sweepers, and walls various Mega Pokemon. Hazards vs longevity is the big decision for this set. This set fits well on Offensive teams as those can have trouble against M-Heracross, M-Pinsir, Talonflame, and Sand Rush Excadrill while Cofagrigus can stop them from doing anything detrimental. Cofa also doesn't give up a lot of momentum either as it can just Haze boosts away or set hazards of its own which makes KOing it a priority for the opponent. It could work well on stall teams too as it fits nicely into a defensive core of Chansey+Ghost-type+Fighting-type (I'd personally opt for Chesnaught in that core to have 3 types of entry hazards).
Personal Opinion of the Pokemon/Conclusion:
Cofa can make for a decent Trick Room user with Nasty Plot but Trick Room's gimmicky in itself and Sticky Web is a far easier to manage method of playing with speed tiers (which Defensive Cofa can Spin-Block for). Don't bother with Specially Defensive sets to wall Starmie, Dusclops does that better. Toxic Spikes are a lot more reliable than some might think since M-Venusaur and Amoonguss are the only remotely common Pokemon that remove them on switch and is seen almost exclusively on stall and even then some stall teams prefer M-Charizard X over Venusaur. Only use Cofa if you need to Spin-block, Mummy's a very nice perk to have but there are more reliable walls out there.