I haven't read the whole forum on this subject so maybe i"m just repeating what has already been suggested. After all these years I've found something I like better than a seam ripper. On the package it is called a Snap Off Blade Cutter -- I'd always used them for trimming wall paper. But now always have one hand to rip seams open. If the blade gets dull, just break off the last segment of the blade and you have a new, sharp blade to work with - and you can retract the blade when not using it.
Derla