Mirrodin Besieged brings a new mechanic to play on the Mirran side of the battle in the form of battle cry. Battle cry gives each other attacking creature +1/+0 and it triggers for each attacking creature who has battle cry. Where the exalted mechanic encouraged attacking with a single creature, battle cry encourages attacking with a lot of creatures.
One of the new artifact creatures from Mirrodin Besieged that has caught my eye, and many others, is Signal Pest. On his own he doesn’t do much. However, once he has buddies to attack with, he gets interesting. Having psuedo-flying means that he’s a bit harder to kill than your standard one mana creature and that maybe he’ll stick around through a couple of attacks.
I feel that this card might prove sometimes useful in Limited formats, though it is not a strong enough inclusion to make most cubes. A cube running only commons and uncommons might find this card to be strong enough to find a place for it. If there’s any real hope of this card being good right now, I feel that it would be most applicable in the Tempered Steel deck in Extended. This deck debuted at Worlds 2010 and was exciting enough for the coverage team to produce a video deck tech about it. The deck itself is pretty tight, so finding spots for Signal Pest seems to be a challenge. I think the best candidate might be Ornithopter or maybe cutting one each of a number of different cards to make room. This deck wants to attack and Signal Pest feels right at home with that mentality.
Overall this is an interesting card that might find some specialized play in constructed, but it will likely be used more in limited where it can be drafted specifically for an aggressive archetype using battle cry.