Juggernaut

Metroid Example
     DM: "The icy creature in front of you is armored in a thick, frosty shell that resists most of your attacks. You might be able to get it to expose the weaker, unarmored parts of its body, though... I'd say Athletics, Acrobatics, and Perception would be applicable."
     Samus: "Can I start off with a Bluff check to trick it into charging past me instead?... 22."
     DM: "Sure thing. That's a success. The beast rushes at you blindly, and I'll give you a +2 on your next check because it was a clever idea."
     Samus: "Great! I'll try to use... hmm, Perception to identify the weak spot befre the creature can react. Oh, darn, that's only a 16 even with the +2..."
     DM: "Failure. The creature twists toward you before you can get a clear line of sight, but you're pretty sure it's weaker in the back..."
     Samus: "Oh, you mentioned Acrobatics, right? I'm actually pretty good at that one. I'll try to tuck and roll past it for the rest of my checks so I can get behind it. 23... 21... 27."
     DM: "Nice! You tumble past the creature as it struggles to keep its eyes on you and deliver a quick blast to its back. The icy shell around it cracks and starts to melt - it's not going to have as easy of a time shrugging you off now!"

Prerequisites:

Juggernaut Elite Soldier
Defenses +2 AC; +2 Fortitude
Resist 5 all at 1st level, 10 all at 11th level, 15 all at 21st level
Saving Throws +2
Action Points 1
HP +8 per level + Constitution score
Powers
Hidden Vulnerability
Choose a set of 2 or 3 skills appropriate for tackling or analyzing the juggernaut. For example, Arcana and Perception for a magically-shielded beast, or Athletics and Acrobatics for a massive, climbable creature. An adjacent opponent can engage in a skill challenge to discover or expose the juggernaut's weakness. DC 20 + 1/2 level, Complexity 1 (4 successes before 2 failures). Success negates all resistances the juggernaut has. Failure triggers the Knockback power (see below.)
Knockback (immediate reaction when an adjacent opponent fails the Hidden Vulnerability skill challenge; at-will)
The monster makes a basic attack against the opponent who failed the skill challenge. On a hit, the target is pushed 2 squares.
Resurgence (free when first bloodied)
The monster regains its resistances if they were lost. Opponents may now attempt the Hidden Vulnerability skill challenge again.