If using bamboo or wooden skewers, cover with water and let soak for at least 30 minutes.
Combine lime zest, lime juice, sugar, oil, chili powder, and salt in a medium bowl. Whisk to dissolve sugar.
I like to use head-on shrimp as I find they have more flavor. I leave the heads and shells on and rinse them well in cold water. If you'd rather get headless shrimp that's fine too. Peel and devein the shrimp if you'd like, either way works. Toss shrimp in marinade, cover, and refrigerate for an hour.
Start the grill and let it heat to medium-high.
Drain the skewers if soaking and thread papaya and shrimp (1 shrimp and 2 papaya pieces per skewer for appetizer bites and more for meal-sized portions) on the skewers. Saving any leftover marinade for brushing.
Grill skewers, brushing with marinade occasionally until shrimp are pink, firm, and cooked through. The timing on these will depend on how hot your grill is. Mine was pretty cool, so they took about 10 minutes.
Sprinkle skewers with a little habanero salt if you'd like and serve with lime wedges.