Gethin and Celyn have a huge selection of toys. I often buy ones designed for parrots that hang from the top of the cage and they can chew on the woody bits if they want. They've also got a few cuddly cat toys on strings that hang in their cage. They really seem to like toys with bells or chimes on them. If I'm late with breakfast, they certainly let me know in a very noisy way!
Their favourite toy has to be the sofa. On a whim a few years back, I bought one of those dog bed's shaped like a fold out sofa. Well, they loved it and I've now got a couple so I can put one in the wash and still have one. They often crash out on it and get very upset if I forget to put it back in after doing "room service." It can get quite grubby, but so far, I've only had one disintegrate in the wash. I'll post a picture when I can reduce the size enough to post it.
Oh, and oddly enough, I accidentally dropped a small plastic frog into their cage - you know, like a rubber duckie, but frog shaped. They seem to like that as well. No matter where I put it, they seem to put it back on the sofa. I'm not sure what they do with it when I'm not there!
They also like cardboard tubes they can run through and chew on and willow rings, which they destroy in a matter of days.