Cut one pineapple into 8 rings by slicing the pineapple. Cut the other pineapple into spears by cutting it in half longways. Then cut those pieces in half longways to make quarters, and then in half once again to make 8 spears.
Preheat the grill to medium-high heat (or start your coals for a charcoal grill) and lightly coat the grate with vegetable oil.
In a medium bowl, mix together the melted butter, brown sugar, honey, cinnamon, and salt until you have a sauce.
Brush the sauce all over the pineapple rings and spears with a pastry brush.
Grill the pineapple for 2-3 minutes per side. Brush each side in sauce again before flipping. For the rings, rotate 45 degrees to get a nice diamond grill mark pattern.
Remove from the grill and serve warm as is or with vanilla ice cream.