Smithing

When you hit Paragon level (11th), if you have the relevant weaponsmith or armoursmith practice you can reforge +1 or +2 gear to +3. This will normally take a good deal of time though (possibly weeks), unless you have the cash to buy a lot of residuum. [:D] If the result is an item above your level it will take both time and money.

Examples:

Reforge +2 weapon to +3, this would give you +1 to hit/damage until 12th level (when your Inherent attack bonus goes to +3), and a permanent extra d6 on critical hits.

Reforge +2 masterwork plate (+9 armour bonus, +2 enhancement bonus) to +3 masterwork plate (+10 armour bonus, +3 enhancement bonus): This would give a +1 enhancement bonus to AC until 14th level (when your Inherent AC  bonus goes to +3), and a permanent +1 armour bonus to AC.

Example:

Level 11 PC with +2 masterwork plate & heavy shield: AC 10+5(level)+11(+2mwplate)+2(shield)=AC 28.
Level 11 PC with +3 masterwork plate & heavy shield: AC 10+5(level)+13(+3mwplate)+2(shield)=AC 30.