I use the Havels ultra pro seam ripper - almost looks like a curved and pointed Xacto blade. Easy to pick at one stitch and sharp enough to rip long seams (not that I EVER have to do that)

It is pricey but worth it.

I have the table top seam ripper and it's great for cutting the chain stitching between sewing quilting pieces. It's weighted and with the straight standing ripper on top, it's great for this purpose.