I wear Shimano MT-20Ds (link), which are basically their bottom-of-the-line MTB shoe, and can be found very cheap.

Pros:
-look like normal shoes, I wear them at work often
-almost no clicking. They click on uneven surfaces but not on normal floors
-walkable despite being very stiff
-cheap. buy them on sale.

Cons:
-The tie up laces don't get tight enough on my skinny, flat feet, so when skipping hard or climbing there is noticeable stretch as the foot leaves the floor of the shoe. This might bother you.

I also have a pair of Specialized body geometry road shoes that fit like a glove, and are very comfortable on my flat feet, but they are road shoes and useless for city riding.

If blending in is important to you they are nice shoes and have held up well, but if you want mostly a riding shoe I'd go for a velcro or ratchet.