While I was working with FlashDevelop I used the duplicate & delete line shortcuts a lot.
Since I’ve been working with Unity3D/MonoDevelop I missed that, thought there is no way to do so. But… there is. And it’s even cooler. 🙂

If you have no text selected in MonoDevelop the copy, paste & cut shortcuts are simply effecting the whole current line. So, to duplicate a line press Cmd + C then Cmd + V. To delete a line just cut it by pressing Cmd + X. If you are on windows use the Ctrl-Key instead of Cmd.