My 98 C-Class has the warning triangle mounted in the bootlid and the first aid kit in the parcel shelf.
The law as to what must be carried varies throughout Europe. The previous posts about German legislation are correct. In France and most other European countries you must carry a spare bulb kit, too. In fact this is a very useful piece of kit and I'd recommend carrying one. In Spain, if the driver wears spectacles, he must carry a spare pair.
Some European countries require the driver to have his driving licence, insurance documentation and certificate of ownership available in the car at all times which is a bit draconian (France is like this, but then in France one gets the feeling that the cops are more dodgy than the crims).
1999 SL 500
1993 320 TE
1986 500 SEC