Unfortunately, I think most of the cool magic items in 4e are just carry-overs from earlier editions. Things like the portable hole, or the bag of tricks.
4e (and, to be fair, 3e) have kind of ruined magic items for me.
I like Green Thumbs also. A strong way to be a controller for one encounter a day.
I also like the skull (ob) in P2 or P3 that has nice resists and a couple nice wizard powers. The ribald jokes about the skull around our gaming table are quite amusing. YMMV.
The Thing I like about 4e magic weapons is that you can get cool weapon properties before 7th level. You spend a lot of adventuring time with a +1 sword in earlier editions.
for specifics I like the determined property: add strength mod to range for a thrown weapon? yay! although the daily power is medicore.
I also really like the master's wands - more in the hands of high int warlocks or other int based characters. push on a magic missile, extra effects from dire radiance.
I like the Throwing Shield, too.
There's a belt from a Bazaar of the Bizarre that lets you throw rocks at things for a decent amount of damage. I'm a fan of that.