I like Sniping on Dagobah. Lot's of places to hide up in them trees. There's also some fairly good long stretches to shoot from too.
My fave map prolly has to be Kamino.. always has been. If we're taking mod maps into account.. The Rise of the Empire maps are phenominal. Bespin Cloud City is a good ole standby, and is always in the favorite list as well.
Rogue52 alludes to specific units too.. that's a good point.. While I enjoy sniper on kamino.. not really the map to go engi.. If I'm going Engi.. my favorite map would be Polis Massa. Same with going Heavy.. My favorite map when playing a Heavy, would have to Mygeeto.