Whats you favourite ceramic?  

Bitossi
I'm collecting the Italian Bitossi ceramics in blue.

Bit of a mix
I, too, have been collecting the Bitossi stuff for a while. I love the stylized animals. I also buy nice studio pieces when I find them. There are so many nice ceramics made by little known, or unknown artists that are just wonderful. Often I'm attracted to pieces with nice subtle glazes on simple forms. They can often be purchased very inexpensively and are just as nice as some of the "name" pieces we have.

Maybe that's
Koen would have some ideas ? He knows the field. . .

I've always liked Poole...
I've always liked Poole Delphis - Here's one of mine below.

some belgian suggestions
jos devriendt
charles catteau
antonio lampecco
pieter stockmans

WOW canisters
Another Belgian suggestion (not that I am chauvinistic, no way)
canisters by Vincent van Duysen for When Objects Work.

wow theyre really nice.
wow theyre really nice.

I could probably...
fill the whole page with names and I certainly agree with some of the ones mentioned already: Piet Stockman, Antonio Lampecco (my former teacher) etc. but also younger people like Tonfisk. One that I like both for his industrial and artisanal production is Marek Cecula.
http://www.modusdesign.com/sites/products_new_preview.php

MAtteo thun cuculus canorus...
MAtteo thun cuculus canorus and columbina spheroida tea pots

Tonfisk
Tonfisk is indeed pretty amazing ..
http://www.designaddict.com/design_index/index.cfm?fuseaction=producer_s...

Heath ceramics
Heath ceramics do pretty lovely dinnerware, vases etc too
http://www.heathceramics.com/shop/heath_reg_lines.php

Masahiro Mori
Japanese designer Masahiro Mori is a very famous Japanese designer who makes the most gorgeous cermacic sets. I still pine after a set I neglected to buy a couple of years ago.
http://www.chatchada.com/site/html/p_mori_collection.html

small time artisans
Some unknown artisans make the most beautiful things. I love Mark Stafford's small pets in a single glaze. (The link is to his Etsy shop)
http://www.etsy.com/shop.php?user_id=5205773

.. used as a blank canvas for art
e.g. the Illy series