Here's a quick tip showing how you can easily make a teardrop shape without messing around in the node editor.
1. First, using the Default Shapes, draw a circle. It doesn't matter how large but make sure it's circular and not an ellipse.
2. Second, draw - via Special Shapes - a heart. Give it the same width as the circle and make its height 1.5 times the circle's height/width.
3. Align the shapes along their vertical centre and manually move them vertically until they look like figure 3.
4. Drag-select both shapes and choose "Item -> Path Tools -> Path Operations…", make sure you've got "Unites the shapes" selected - it doesn't matter which way round the shapes were selected - and OK the dialog.
You should now have a teardrop, which you can either flip or rotate so it's the right way round.
Once you have the basic shape you can use it for different things.
Example 1: Add a radial gradient fill and some embellishments to make it look like a water droplet.
Example 2: Draw a smaller circle and use the Path Operations to Subtract that from the teardrop, then rotate the result by 180deg and give it a shadow to make a nice "map pin".
I'm sure you can think of more interesting uses for it.