Lighting Dmg Weapons Have 25% Armor Penetration???

I asked someone what the best upgrade is after I bought a sword and he said lighting cause it has armor penetration is this true or just a false lead.

Some of the lightning skills (air magic line) have armor penetration, but never heard of weapons that had any.

At one time (early beta) lightning damage of any kind, including weapons, got a penetration bonus on warrior's armor, but that has been removed. Now, as C-Tzar said many lightning elem. skills give 25% on armor. Also, elemental damage is especially effective against warriors as it ignores their armor's defense bonus against phys. damage (and, alternately, it is less effective against rangers).