win a virtual fencing match (against your fellow stack exchangers)
Python

En garde!

My warrior combines unpredictability with a keen eye for weakness in his opponent's stance.  He's pretty confident he'll be able to dispose of aggressive foes but his trainer (me) may have failed to anticipate certain scenarios or, perhaps more worrying, may have misinterpreted the rules (bugs!!).

Anyway I'm new so hopefully this is an ok format for the code:

from random import choice, random

def cleverly_pick_move(me_allowed,op_allowed,opp_last_move=None) :
    """ Behold the genius you're up against!
    Pretty much everything else is just flavour text or match rules
    so you'll probably only want to read this...
    """
    heights = ['head','chest','feet']
    rand_choice = lambda a,h : {'type':choice([t for t in a if a[t]]),
                                'height':choice(h)}

    if opp_last_move is None or feeling_like_a_lucky_punk():
        return rand_choice(me_allowed,heights)

    if sum(1 for x in op_allowed if op_allowed[x]) == 3 :
        for i in op_allowed:
            if not op_allowed[i] :
                weakness = i
                break
        return {'type':exploit_weakness(weakness,me_allowed),
                'height':choice(heights)}
    return rand_choice(me_allowed,heights)

def exploit_weakness(weakness,me_allowed) :
    moves = ['attack','parry','lunge','block']
    for i,move in enumerate(moves) :
        if move == weakness :
            if me_allowed[moves[(i+1) % 4]] :
                return moves[(i+1) % 4]
            break
    if me_allowed[weakness] :
        return weakness
    return choice([x for x in me_allowed if me_allowed[x]])

def feeling_like_a_lucky_punk() :
    return random() &gt; 0.8

def main():

    this_round = 1
    opp_last_move = None
    score   = {'myself':0, 'the blaggard':0}
    quips   = ['blaggard', 'fool', 'scum', 'raggamuffin']
    adverbs = ['deftly', 'skillfully', 'gracefully', 'clumsily']

    me_allowed = {'attack':True,'block':True,'lunge':True,'parry':True}
    op_allowed = {'attack':True,'block':True,'lunge':True,'parry':True}

    while (this_round &lt;= 50 and
           all([points &lt; 3 for points in score.values()])) :

        if this_round == 1 :
            move = cleverly_pick_move(me_allowed,op_allowed) 
        else:
            move = cleverly_pick_move(me_allowed,op_allowed,
                                      opp_last_move=opp_last_move)

        print "Our hero %s %ss at the %s's %s" % (
            choice(adverbs),
            move['type'],
            choice(quips),
            move['height']
            )
        print "We await the %s's response..." % choice(quips)
        print "Our hero's move: " + (move['type'][0]+move['height'][0]).upper()

        opp_move = parse_move(raw_input("Opponent's move: "))

        outcome,me_allowed,op_allowed = get_outcome(move,opp_move,me_allowed,
                                                    op_allowed)
        if outcome == 'WIN' :
            print "Our hero pulls off an excellent round!"
            score['myself'] += 1
        elif outcome == 'LOSE' :
            print "Never before have we seen such blatant cheating!"
            score['the blaggard'] += 1
        else :
            print "Our hero is clearly toying with his opponent as he allows \
a drawn round."

        print ("""The score after round %d:\nOur hero:\t%d\nHis opponent:\t%d""" 
                % (this_round, score['myself'], score['the blaggard']))
        opp_last_move = opp_move
        this_round += 1

    print "Match over, surely the victory is mine!"
    print """Final score:\n
             Our hero:\t%d\nOpponent:\t%d""" % (score['myself'],
                                                score['the blaggard'])

    if score['myself'] &gt; score['the blaggard'] :
        print "My victory was inevitable!"
    elif score['myself'] == score['the blaggard'] :
        print "An even match! Huzzar!"
    else :
        print ""    
    return

def reset_allowed(dictionary) :
    return dict((x,True) for x in dictionary)

def get_outcome(mymove,opmove,me_allowed,op_allowed) :
    result = ''

    if not me_allowed[mymove['type']] :
        print "Whoops, I forgot I couldn't do that..."
        result = 'LOSE'

    if not op_allowed[opmove['type']] :
        print "Haha! What a clutz!"
        result = 'WIN'

    if mymove['height'] != opmove['height'] :
        print "The combatants flail at each other with little effect!"
        print "They'll have to try something else next round!"
        result = 'DRAW'

    if mymove['type'] == opmove['type'] :
        if mymove['type'] in ['attack','lunge']:
            print "The combatants' blades clash dramatically!"
        else :
            print "Both combatants take a moment to practice their \
defensive stance..."
        result = 'DRAW'

    if result :
        me_allowed, op_allowed = (reset_allowed(me_allowed),
                                  reset_allowed(op_allowed))
        if mymove['height'] != opmove['height'] :
            me_allowed[mymove['type']] = op_allowed[opmove['type']] = False
        return (result, me_allowed,op_allowed)
    else :
        return compare_attacks(mymove,opmove,me_allowed,op_allowed)

def compare_attacks(mymove,opmove,me_allowed,op_allowed) :
    """
    0 A &gt; P 1
     ^  x  v
    3 B &lt; L 2
    """
    print "Our hero %ss, his opponent %ss!" % (mymove['type'],opmove['type'])

    move_val = {'attack':0,'parry':1,'lunge':2,'block':3}
    result_num = (move_val[opmove['type']] - move_val[mymove['type']]) % 4
    results = ['DRAW','WIN','DRAW','LOSE']

    me_allowed, op_allowed = (reset_allowed(me_allowed),
                              reset_allowed(op_allowed))    
    if result_num == 1 :
        print "Our hero easily outwits his foe! *Huge cheers from crowd*"
        return ('WIN',me_allowed,op_allowed)
    elif result_num == 3 :
        print "Our hero graciously allows his opponent a charity point.\
*A torrent of boos from the crowd*"
        return ('LOSE',me_allowed,op_allowed)
    else:
        # Combatants drew and will have their moves restricted next round.
        if mymove['type'] in ['attack','parry'] :
            me_allowed['attack'] = me_allowed['lunge'] = False
            me_allowed['parry']  = me_allowed['block'] = True
            op_allowed['parry']  = op_allowed['block'] = False
            op_allowed['attack'] = op_allowed['lunge'] = True
        else :
            me_allowed['parry']  = me_allowed['block'] = False
            me_allowed['attack'] = me_allowed['lunge'] = True 
            op_allowed['attack'] = me_allowed['lunge'] = False
            op_allowed['parry']  = op_allowed['block'] = True
        return ('DRAW',me_allowed,op_allowed)

def parse_move(move_string) :
    m_types = {'A':'attack','B':'block','L':'lunge','P':'parry'}
    m_heights = {'C':'chest','H':'head','F':'feet'}

    move_string = move_string.strip().upper()
    if not move_string :
        print "Couldn't understand your input: %s" % move_string
        return parse_move(raw_input("Opponent's move: "))

    if move_string[0] not in m_types :
        move_string = move_string[::-1] 

    try :
        move = {'type':m_types[move_string[0]],
                'height':m_heights[move_string[1]]}
        return move
    except KeyError :
        print "Couldn't understand your input: %s" % move_string
        return parse_move(raw_input("Opponent's move: "))

if __name__ == '__main__' :
    main()