The Pirates! Land Lobber is a lot more polished than your run of the mill free flash game, probably because it was made by Wallace and Gromit producers Aardman Studios, as a means of drumming up support for the movie The Pirates!
Land Lobber is a rail shooter, in which you use the mouse to hit targets onscreen, which sometimes appear as dancing pirates or cardboard cutouts of Queen Victoria. At first, you're going to have problems hitting the targets, since the cursor is wobbly and it takes time to reload, but keep at it. The points you earn inbetween rounds can be used to purchase upgrades for your throwing arm, as well as buy guns. It's the upgrade mechanics that put that really make the game soooo addictive. You'll be spending quite some time with this game.
Play The game directly from your browser, after the cut: