Would you like to sign up to our newsletter? o [[[ OK!! ]]] o No I'm an idiot and I don't want to save money or hear about the latest job offers that may change my life
(Exaggerated slightly.)
I'm not sure this if this technically counts as a dark pattern as it's fairly transparent but I find it is very annoying because it is an attempt to force a user to state an opinion they probably don't hold if they don't want to sign up for whatever service.
I assume it does work or it wouldn't spread so widely but exploiting people's reluctance to criticise themselves seems quite unpleasant: I imagine this affects people with the weakest self-esteem the most.