Can't we all include a short motivation why we like these manga? Otherwise it'll just be pointless name dropping, no different from the threads in The "What" Board. Who knows, maybe your motivation will help to get someone interested in your favourite series?
In order:
1. Cardcaptor Sakura - because it's so damn adorable, and I love how it gently pokes fun at the magical girl shoujo genre, as well as its message about acceptance.
3. Tokyo Babylon - which I would proclaim CLAMP's best work to date. The serious, much more real life-related themes than what is usual in CLAMP works, the social critism... I love that.
2. RG Veda - because it contains everything that a CLAMP manga should have - tragic, twisted love, gorgeous artwork, destiny and yes, even eye losses!
4. TRC - probably because it's the first unfinished manga I've ever followed, and thus during the years I've grown to care so very much for the characters, but also because of its hopeful message and how the characters grow during the series.
5. xxxHolic - the lovely artwork, and the philosophy.
Ahem. I do read other manga besides CLAMP, I just... don't like them as much.