I like keeping a collection of my favorite TV shows and Movies along with the subtitles. For a single playback, I won't mind fixing the subtitle from the player's settings, even though its frustrating most of the times, but while making a collection, you need perfect subtitles. Finding the correct one is not an easy task and neither is editing it. This is where a subtitle-editor comes in handy. Gnome-subtitles is one such tool and by far my favorite.