I'm sick of buying toys for DD that she has no interest in. :( I've had better luck recently with just letting her play with household stuff.
Recently she got her hands on one of those 16 oz water bottles with the really thin plastic and she looooooooooooves it. It kept her entertained for a really long time - chasing it across the room, crinkling it, chewing on it. I tried to "improve" it by adding some dried small pasta in it to make it a shaker but I'm not sure she likes the improvement. :/
I've also given her an empty tissue box (to put/pull toys in/out), measuring cups and a potato masher....she's okay with those but doesn't love them like the water bottle.
And, of course, there are the things *she* wants to play with but I work to keep away from her (remotes, cords, etc).
What "toys" do you let your LO play with that s/he loves?