Ok, so you can get a tower shield to be under 20 lbs by being small and using darkwood. And Glove of the Master Strategist is basically glove of storing but better and 1/3 the price (3500 gp, also gives true strike 1/day). So here's the basic idea I have:
Keep the tower shield hidden away inside glove, ready an action to attack someone when they melee attack you.
-As they approach, ready triggers, you free action (as part of the ready) shield out to hide behind, negate their attack
- Free action shield back into the glove (as part of the ready) and take your own attack
- If he's not dead, you get to full attack him next turn before he can act again.
For added cheese, use a 2H reach weapon, free action'ing your shield hand on and off as needed to hold the shield. Then you can also get an AoO as he comes in. For even more fun against a charger, add Lion Spirit Totem Barb 1 (pounce), Cometary Collision feat, and Steadfast Boots (if not using a longspear).
*Shrug* Just trying to find outlandish ways to break a vastly ridiculed piece of equipment.