What can I use as a replacement for cumin?
The problem is that a lot of substitutions are based on what you have on hand.

For instance, I have both liquid smoke and smoked paprika, both of which would add that smoky quality that people associate with cumin.

We also need to consider what other ingredients are going into the dish.  I have spice blends that contain cumin in varying degrees (garam masala, taco seasoning, a rub for ribs), and if they contain other ingredients that I might be using anyway, I'd consider replacing all of them with the spice blend.