People:
* David
* Diana
* Dwayne
* Dakota
* Danielle
* Drake
* Dylan
* De Niro
* Da Vinci
* Darwin
Places:
* Denver
* Detroit
* Dubai
* Dublin
* Denmark
* Dominican Republic
* Delaware
* Disneyland
* Death Valley
* Dachau
Things:
* Disney (company)
* Dell (company)
* Dodge (car brand)
* Dunkin' Donuts (company)
* Decade
* Doctor Who (TV show)
* Days of Our Lives (TV show)
* Declaration of Independence
* Dow Jones (stock market index)
* Doberman Pinscher (dog breed)
Other:
* December
* Thursday
* Dreamland (a place in dreams)
* Dracula
* Dumbo
* Daenerys Targaryen (character from Game of Thrones)
This is just a small sampling. There are countless other proper nouns beginning with the letter "D".