IMO 21/15 and 24/15 are the best STR shielder build.
I agree, you get access to a few better shields (ie. Huscarl) with 15 Agility plus an extra athletics (for shorter weapons like axes and picks). For weapons i personally like the following
Italian Sword-Good all around sword, not to expensive either
Grosse Messer- Fast, strong, but with low reach and little thrust damage
Broad One Handed Battle Axe(my personal favorite)-Hits hard, tears through shields, but low reach and speed is not remarkable
Steel Pick-Fast, strong, pierce damage(tin can opener), VERY SHORT, people will complain about you having no skill
All in all, it is up to you, these are just the ones i have had the most success with myself, i agree with Christo saying that you should carry two weapons, but it can be a little expensive to maintain two weapons(i went through a massive period of gold loss when i had Italian Sword+Steel Pick, i was wearing very heavy gear on top of that).
For shields, i currently use the Heavy Kite Shield, it has good durability, body armor and size, all for only one slot, it is quite thin though. The Huscarl is good(very large, durable lower than the heavy kite though, very good body armor) especially if paired with the pick(they can't see your attacks as easily).
But just choose what you like best in the end.