Sadly, it won't make the holiday shopping season, but toy company NECA's replica Half-Life 2 gravity gun will be available for purchase next Spring.

It's 1:1 scale, and as you can see from the prototype below, lights up as well. Since this is the same company behind the replica Portal guns, you could probably expect some sound effects as well.

1:1 Half-Life Gravity Gun Coming From NECA In 2013 [TNI]