Jackals are known to be shield wielders and snipers you will come across while playing the Halo Campaigns. Killing 1000 will unlock this achievement. If you plan on going for the other achievements this will come naturally.
If you want to go out of your way for this one, you will want to play Halo 1-3 over Halo 4 because Halo 4 is more about Prometheans than covenant (Which Jackals are part of the Covenant).
I found a very educational video for to watch and learn about jackals, and possibly a good laugh, by Teh Spearhead. (The animation on the cover is not the animation through-out the video)