A lot of times I'm in a situation similar to this:
1. <Line 1> 2. <Line 2> 3. <Line 3> 4. <Cursor is here> 5. <I want to copy line 1 here>
An easy solution is
mm:1<CR>yy`mp - that is, make a mark at line 4, go to line 1, copy it, go back to the mark, and paste.
Is there a shorter/more fluid solution to this? I do this often enough that I'm happy to make a mapping for it.