Ring of Silent Spells (MiC page 127) doesn't get enough recognition. Once per day, you can cast a quickened Silence spell at caster level 5 centered on yourself. This already makes it fantastic for stealthy types, but it also allows the wearer to cast up to 3 spells of 3rd level or lower as though they had applied Silent Spell to them. It's only 2,000 gold, making it one of the cheapest magic rings.
5 minute duration, swift action to activate, and 20ft radius is also enough to ruin the day of enemy spellcasters.
Honestly, I would recommend it as an addition to Bunko's.