Preheat the oven to 350°F. Line two baking sheets with parchment paper.
In a large mixing bowl or the bowl of a stand mixer, beat the butter and brown sugar on medium speed until light and fluffy, about 3 minutes.
Add the eggs, one at a time, beating until smooth after each. Mix in the vanilla.
In a separate bowl, whisk together the flour, oats, baking soda, cinnamon, and salt.
With the mixer on low, gradually add the dry ingredients just until combined and no dry streaks remain.
Fold in the pretzels, peanut butter M&M's, peanuts, chocolate chips, and chocolate chunks.
Use a medium cookie scoop or two spoons to drop equal portions (about 1 1/2 tablespoons) of dough onto the prepared baking sheets, spacing them about 2 inches apart. Sprinkle with sea salt.
Bake for 10-12 minutes, rotating the pans halfway through, until the edges are lightly golden and set, and the tops no longer look wet. The centers should still look slightly soft—they’ll firm up as the cookies cool.
Remove from oven and let cool on the baking sheet for 5 minutes. Transfer to a wire rack to cool completely, 15-20 minutes.
Serve immediately or store in an airtight container.