The other toy line I collect in force is Lord of the Rings. I pick up the Simpson line for my son ( I have to find wave 12 Moe and wave 13 Stephen Hawkins and that will bring me to the end of summer for free car washes
).
I (along with my daughter) also collect Mattel's "Kelly" dolls (Barbie's baby sister). The output on these little darlings (and endless variations) puts all other lines to shame.
My son also has a large GI Joe collection along with MOTU, TMNT, Batman and X-men. I think his X-men collection is the largest (Joe might be pretty close though). The reason I mention his collection is that we both pursue it. I started back in the 80's when my kids were born, buying up toys and keeping them until they were old enough to open them and play. Nothing is in its original boxes (it's all sorted and stored in giant Rubbermaid containers) but Jeff knows exactly what figure goes with what character. Every so often he'll talk about selling one part or another and then when it comes right down to it, he can't part with any of it. I keep filling in missing (or broken) guys here and there and I am quite sure that there is nothing left to purchase for the old X-men line as well as the TMNT.
It's been such fun over the years, collecting all this stuff and watching my kids play with the toys but also keeping them in some what of a "clean" stage. I've instilled the collecting bug in my kids and I hope they can pass it on one day.