My biggest regret would be letting all my domains lapse back in 2002 when I went travelling. There weren't any "mega" domains in the portfolio, but I'd certainly like to have some of them back now!
I once owned SydneyHotels.com.au which I hand reg'd for $50, held it for 12 months then let it drop. Also had LakeMacquarie.com.au which I forgot to re-register.
* Be at least 2 or 3 characters long, dependant on the namespace, EXCLUDING the namespace. For example:
o z.com is invalid as the length of the domain without the namespace (.com) is only 1 character
o yes.com is valid as yes is at least 2 characters long
* Be no more than 63 characters INCLUDING the namespace
* Contain only letters, digits, and hyphens. For example:
o It's-1-Bad-Domain.com is invalid as it contains illegal characters
o its1gooddomain.com is valid as it does not contain illegal characters
o its-1-good-domain.com is also valid as it does not contain illegal characters
* Not start or end with a hyphens. For example:
o -1-bad-domain.com is invalid as it begins with a hyphen
o 1-bad-domain-.com is invalid as it ends with a hyphen
o 1-good-domain.com is valid as it does not begin or end with a hyphen
Please make sure your Domain Name follows these rules and search again
Note: This is intended for use as a rough guide only and may not be representative of the namespace(s) you are after.