Earth, Level 4, [Warrior/Effect]
ATK: 1700, DEF: 1600
DBT-EN002, Super Rare (Yu-Gi-Oh! Destiny Board Traveler Promo)
"When this card is destroyed as a result of battle with your opponent's monster, remove from play both this card and the opponent's monster that destroyed this card."
D. D. Assailant is one of the three Different Dimension monsters, including the very popular D. D. Warrior Lady, and the not-yet-released D. D. Warrior, who was available in the Worldwide Edition game as "Dimensional Warrior". These three monsters all feature effects which remove themselves and the opponent's monster from play, and they, together with a host of other cards like Dimension Fusion and Return from the Different Dimension, have brought about the rise of Remove From Play effects and decks which abuse them.
D. D. Assailant's basic statistics are average. 1700 ATK is a bit substandard, but its effect helps cover this. 1600 DEF is unfortunate, since it makes it unsearchable. Its Earth attribute is ok, but its Warrior Type is excellent. Warriors are extremely strong in the current metagame, with so much support being thrown at them in tins, promos, and recent booster packs. Just look at these three cards today -- all of them are very good and all of them are Warriors!
You could put D. D. Assailant in face-down Defense Position to surprise your opponent, which is great and very strategic. You can also put it in face-up Attack Position. As I mentioned, the ATK is low, but your opponent has to beat 1700 ATK in order to destroy it, and that will cost him when his card is removed from play. Sometimes, obviously, the opponent won't flinch and will go ahead and attack anyways. But if you gauge the play situation carefully, you may catch your opponent at a point where he cannot afford to do this, and then you can gain the upper hand in field presence, turning everything around.
D. D. Assailant goes into the Great catagory, I think. Although D. D. Warrior Lady is perhaps more flexible since her effect is optional, she also has a harder time pretending to be a beatstick. Forum arguments on which is better seem to be very common, and I think the answer is that neither is "better," they're just situational, and thus work better than each other part of the time. Putting both in a deck, especially one focusing on Remove From Play effects, wouldn't be out of line at all. At any rate, this card has an excellent effect and that's what gives it a high rating.