The vibrations a speaker can produce could be very useful for haptic feedback. If this is a speaker modified for that purpose with a thicker, heavier membrane I think it would work very well
Think like Nintendo's HD rumble. There's certain patterns it can do that make it sound like... sound. In Golf Story for example, the hits with the club, with the hd rumble on, you can perfectly hear the skins of hitting a club even with the audio of the game down. It's strange and great at the same time. The steam controller also used it for those turn on, turn off jingles you could have on, they also sound great.