I Will*

When you pass a wedding in a public space (a park, a beach), make a short list of the ways you could ruin their special day, as well as the pros and cons associated with each approach. You could:

-run through the reception screaming like mad (PRO=you will get attention, it's good to scream it out CON=you'll just be written off as a crazy person)
-confidently walk up to the makeshift alter, start to speak to the bride, and then pass out (PRO=very dramatic, people will wonder what you had to say CON=next steps are tricky to execute, you're boned if there's a doctor around)

While you should probably just let the bride, groom and assorted guests enjoy the celebration in peace, a list will allow you to make a sensible decision

*Make a scene