I know most will opt straight for the offensive sets, but I wonder if a trapping set could be niche enough to work.
Araquanid @ Leftovers
Ability: Water Bubble
Jolly Nature
252 HP / 4 Attack / 252 Speed
- Spider Web
- Toxic
- Liquidation
- Substitute / Leech Life
Due to Water Bubble Liquidation being hard to switch into outside of Water resists or Water immune mons I think this may work. Take something like Alomomola, it switches in thinking it can take the Liquidation hits easily, only for you to use Spider Web (now it can't Regen or Wish pass), then you outspeed it and Sub (it can't break the Sub in one turn) and then you proceed to Toxic it down. Against most bulky Water-types it fairs well with its 68/133 special bulk and immunity to burn, so it's not too bothered by them and doesn't fear burns from Scald. But Toxic is probably going to be pretty expected on most sets, with its movepool being so small, which I guess is a downside.
I think the nature and Speed EVs would depends on which tier it ends up and which things are common there that it could trap (so which it wants to try and outspeed if it can beat them). Might be a bit too gimmicky to work out well but I just wanted to suggest Spider Web on a set really.
edit: whoops, seem to have mentioned someone by mistake :x