For a real professional shooting digitally:
1Dn/1DmkII if you're doing sports/weddings/action
1DsMKII if you can cope with 3 FPS
If you're a beginner learning, get:
1) a flashmeter... with a spotmeter if you can.
2) one strobe on a stand
3) the camera doesn't matter. As long as it has manual controls and a hot shoe for flash attachments.