Another stake user here. Mine is a 1-oz. aluminum semicircular stake left over from some tent or other many years ago. It works just fine. Since my dog also uses it (or rather, I use it for his leavings), he gets to carry it! Only fair since he does his thing twice daily while I need the stake only once a day.
I have also used my shoe heel or trekking pole points, but I've found that the stake is far more effective.
I've found that those cheap plastic trowels are completely useless unless the ground happens to be soft and soggy. After a month of no rain in Pacific Northwest summers, a plastic trowel won't even scratch the surface of the ground.