I have been waiting for this moment...
I use Clubs for SO MANY SNEAKY THINGS.
I have a Household Club where all the sims in the house are in so that I can get boosts for housework and homework.
I have a special club to help my Casanova-type sims boost affairs and dating. Simply add the amour of choice, suggest they do romancy things, and boom you got a relationship!
I've also done mom groups (bit hard, the only allow married sims as a parameter so I had to add by knowing who had kids), a little-rascals club, a sorority and fraternity, and teen dnd clubs.