The Casual/Work Acquaintance
Maybe you have a supervisor or boss that spends time in SL, but you don't know their tastes well enough to know what they'd like as a gift (and consequently feel warm and fuzzy toward you enough to give you a raise). I suggest one of the fine guides to Second Life to be had on Amazon.com. In fact, one of them was co-authored by Our Aimee Weber! And if you can't trust a Massively blogger, who can you trust?
The Close Personal Friend
Surely you have one of these, but after sharing all your copy/transfer items with each other, what is it you don't both already have? The answer to the good gift question lies elsewhere -- not an object, but a service. Pay their land rental fees for 3 months, or be a dear, pay their tier for a year! Nothing says 'I care' better than ensuring that they'll have a guaranteed home for a while. Maybe now they'll let you play DJ in their exclusive club ... an hour of nothing but KC and the Sunshine Band, here we come!
Chances are you noticed their avatar's appearance first, and thought they were something special. People in SL tend to be proud of their avatar's looks -- after all, they probably spent a lot of time getting everything just right. Why not reward that effort with a little statuette of their av from Fabjectory? Heck, order another one just to gaze at adoringly for those times you can't be online together! Ahh, who says long distance relationships can't work?
And finally, for those times when the Grid is down (and we all know how often that is), entice your target with a game card for World of Warcraft! Show them what they've been missing all this time! Who needs friends when you have the Tauren Peanut Butter Jelly Time Dance?