Fixing a dent in a whoffer cone

Adhesive tape works for mild dent. But, generally, a dented dustcap in the center of the woofer does no harm so it is probably better to ignore it.

Is the dent in the cone or the dustcover at the center of the cone?

Another alternative is to "french kiss" the cone. Not just another way to get close to your system, but by gently sucking while puckering your lips against the cone you can work it back out.
Just don't let your spouse catch you doing it. She will undoubtedly grow jealous and never let you have private listening sessions alone anymore.

Fotis_k, you are kidding right ?? But come to think about it, that just might work ... I am just having a hell of a time imagining someone on his/her knees puckering up to the woofers ...

ROTFLMAO

Dont try what Fotis says with electrostats, ,y lips are still healing :)