Being an open source robot arm fan, it would be impossible for me to not look into the uArm by uFactory. This is a really nice open source robot arm being made in Shenzhen. The team executed a very successful Kickstarter last year to the tune on $250k and has continued to support, add new capabilities and revamp the design of their arm. The current arm is a sleek aluminum arm that comes almost fully assembled (just add 10 screws). There is software already loaded on the Arduino compatible control board and all that needs to be done is for the user to download a control app and get going.
My kids and I gave it a whirl with the standard downloaded app last week and I have to say the arm is very easy to control, and while I lost interest with the standard app, my kids went strong all night! The main thing to do is to pick things up with the included suction cup end effector, with the included application you can use the mouse and mouse buttons to completely control the arm. It worked really well and was easy to control. The arm is surprisingly strong, able to pick up heavy items like an apple. Most of the use of the arm is built around the suction cup, however I know that they have a gripper in the works (benefit of it being open source is that you can look at their GrabCad Page). As far as building in your own uses for the arm, they did a good job of abstracting out the the firmware running on the Arduino from the desktop application, which enables you to just focus on the desktop development to get the arm to do something interesting or automated. Currently they have developed a few interesting desktop apps including one for the Leap Motion. What I would like to see is this integrated with scratch or Blockly (I prefer Blocky) so that I can encourage my kids to have the arm do something interesting, like dealing out four decks of Uno cards (a frequent occurrence in our house).
At $299 it certainly isn’t an impulse buy, but this is also a bit more than a toy. It is robust and feels like it could take quite a beating and actually do something useful. I would recommend it if you are interested in playing with open source robot arms.