My favourite forcing trick is that old classic of forcing the same card to different people but making sure they don't let anyone else see it. Then turning everyone's card into the same one.

Once the effect is over you can go straight into something else - I never like to expose the fact that I've used a force - I don't like people to even entertain that they've ever had anything except a free choice. For me it keeps it more magical and you don't have the problem of coming over as a know it all smart alec or of deliberately selling out your audience.