Some missionaries recently shared this activity and I thought I would repeat it here for your benefit. You will need some paper cut outs of swords (make them big enough so you can write on it). You will of course need a pen or pencil for each person and scriptures.
This is based on the scriptures where the Lamanites became changed and Covenanted with the Lord to never shed blood again so they buried their swords and weapons of war. This can be found in: Alma 24:16-17. After explaining the story and what they covenanted you can then hand out the paper swords and pens to everyone present and ask that they write something(s) that they need to bury in their lives (sins or bad habits they need to give up) and then ask that they covenant with the Lord to do so.
You can then collect all the swords (let them crush it up first) and bury it in the back yard so that everyone remembers the event and what they have covenanted.