Question to Rechan -- Did the player at any time say "Captain America" ? Or did he use the words you presented in quotes?
In either case, I'd recommend never to refer to him as Captain America again. It will kill the flavor and tone of your campaign setting. Hence forth, it is a Shield Warrior
Lead by example, if a player uses the term Captain America, gloss over it (don't call attention to it) and just keep using Shield Warrior (or whatever you want).
As to how to implemet it, I'd just take the Fighter Class and just tweak it ..
Note: What follows is somewhere between house-rules and simple reflavoring. You'll find every "new power" listed is actually just taking an existing power and changing the flavor and tone, and then changing one or two things (like keywords to reflect martial melee, etc)
Shield Warrior
Same as Fighter except where as noted.
Remove:
* Fighter Weapon Talent
Gain:
* Shield Talent: You may use your shield as a melee weapon. Gaining a +2 proficiency bonus when attacking with the shield. You do not gain your shield's bonus to defenses when using it as a weapon. Light shields do 1d6+ Str modifier damage, Heavy Shields do 1d8+Str modifier damage. (The first sentence here is really the only "new " class feature - ability to use a shield as a weapon. The rest is just a proficiency bonus when attacking (all weapons get one) and also the damage from improvised weapon rules.
* Shield Bash: The shield weapon counts as a mace or hammer or the purpose of any fighter attack power that has special effects from using a mace or hammer type weapon. (this goes a long way in reflavoring existing fighter powers to work for a shield. since the shield will mostly be bludgeoning people, the mace and hammer are the closest match)
Suggested At Will: Tide of Iron, Shield Toss (new power, see below)
Suggested Feats: Shield Push, Two-Weapon Fighting feats (if want to use the shield in one hand and punch with the other)
New Level 1 At-Wills
Shield Toss Shield Warrior Attack 1
With a fling, you toss your shield in a boomerang like motion, often causing a moment of forced mistep by the enemy allowing allies to strike truer
At_Will * Martial, Weapon
Standard Action Ranged 5
Special: You must be wielding a light shield to use this power
Target: One creature
Attack: Dex vs AC
Hit: 1[W]+Str modifier, and one ally you can see gains a +2 power bonus to his next attack roll against the target.
Increase damage to 2d[W]+Str modifier at 21st level
New Level 5 Daily
Shield Throw Shield Warrior Attack 5
With great force, you throw and spin your shield at odd angles, causing it to bounce off opponents and then return to you.
Daily * Martial, Weapon
Standard Action Ranged 10
Special: You must be wielding a light shield to use this power
Target: One creature
Attack: Dex vs AC
Hit: 2d[W] + Str modifier
Effect: You throw your shield and all your allies gain combat advantage against the target. You can move the weapon up to 10 squares to another enemy's square as a move action. The weapon lasts until the end of your next turn before returning to you. While this power is active, you do not gain your shield's bonus to AC or Reflex. You must have line of effect to your shield at all times or else this power ends immediately.
Sustain Minor: When you sustain the power, repeat the attack. Your allies continue to gain combat advantage against the weapon's target.
that should go a long way to change the flavor.
Note that this does creep on multiple attribute dependancy>
Str for damage
Dex for thrown shield attacks
Con for the bonus on shield bash (since all the mace and hammer attack bonuses are con dependant)
wis if combat supriority comes up a lot
