Some last names that I have heard (which are many) are:
Roque (probably basque in origin)
Polonia
Lantigua (not sure of origin, Spanish or French?)
Olivares (certainly Spanish, not sure from what part)
Garcia (does this one needs an explanation?

)
Sanchez
Encarnacion
Jimenes
Delgado
Bueno
Cardona
Grullon (possibly Basque, but not sure)
Martinez
Peña
Rocha
Rosario
Salcedo
Sena
Valdez (ahem, remember the times of Trujillo? :nervous: , but the people I know are nice, though their history is.... well.... :bandit: )
Zorilla
Mejia (no, not Mr. Baldy)
Hazoury (Probably middle eastern, not sure if Syrian or Lebanese, since those are the two places where most Dominican middle easterners decend from)
Wessin y Wessin
Ramos
Hache
Brugal (need explanation?

he he he)
Bermudez
Sosa
Vicini (Italian, hands down)
Trujillo (not sure of origin... though we all know this one very well... they seem like nice people, but what a difference 40 odd years does!)
Bencosme (not sure of spelling or origin either, but in the times of Trujillo this family practically ruled over Moca in the Cibao, this family even supplied a mayor to that town, completely feared by the everyday person.)
The list goes on and on and on, but this gives a good representations of the different types of last names that can be found in this "tiny" but diverse nation.
BTW, if anyone have concrete answers to the more serious questions I posted here, feel free to answer them. Thank you in advance!