Show Up With a Date Who Wasn't Invited
If you weren’t allotted a plus-one, there's probably a reason. Maybe the couple wanted to only invite close friends and family to keep the wedding intimate; maybe the reception space is small; or maybe there were budget restraints (just one extra guest can mean up to $1,000 or even more depending on catering costs and all the other reception perks meant for invited friends and family to enjoy).
Instead: If you feel uncomfortable attending alone, ask the bride or groom whether there are going to be any other singles at the wedding. They'll get the hint and hopefully seat you next to someone else who’s also going stag.