Excellent question! It's got me thinking ahead to the holidays. :)
Services would be great (dog/housesitting, lessons at something you do well, etc.), consumables, or anything from the Buy It For Life thread. Or even just cash with a nice letter to make it slightly more meaningful than your standard gift card.
I went to a baby shower a couple of weeks ago, and my gift to the soon-to-be parents-of-twins was:
* A small bottle of some fancy and locally made diaper cream,
* A prettied-up gift certificate from me for babysitting,
* A couple of fancy chocolate bars for them, and
* Some pictures our little kids had drawn of their new family.
* All simply packaged in my favorite shopping bag that folds up into a cute little strawberry.
It was totally weird and I got some looks from the other guests, but the parents were completely on board. The mom commented that she especially appreciated the bag because she understood that I was giving up something that I really liked.