I assume you are using the Dhampir feat to be a half-vampire in 4th edition?
To use your blood drain power, you need to grab your opponent. Grabs require Strength to succeed. So Fighters, Paladins, Rogues, Warlords, Barbarians, Wardens, or Swordmages, are all classes that have Strength as primary or 2ndary stats.
Make sure you have a 16 in Strength, and I would give serious consideration to the Improved Grab Feat.
Edit: Which special ability did you want?
If you want Blood Drain, you will want a character with high Strength, and good BAB (+1 BAB/level) since you need to make a grapple check to even begin to drain blood from a target. Grapple checks are BAB + Strength + SIze mods.
From the PHB good classes: Barbarians, Fighters, Paladins, Rangers. From PHB 2: Duskblades, Knights. Complete Warrior: Hexblades,
If you want Charm Gaze, then this abilitiy relies on a high Charisma. Paladins, Sorcerers, cetrtain types of Rogues. Favored Souls, Warlocks, Swashbucklers, Hexblades all need good CHA scores to can benefit this power.
If you want the Children of the Night power, then anything nature themed should do the trick: Druids, Rangers, Dargon Shaman, Sprit Shaman, Favored Souls, or Scouts. The animal summoning has no stat requirements. So really any class will work. I'm just trying to look at it from an RP perspective.
The only class to stay away from is Cleric. Traditionally the foes of undead, with thier ability to turn undead.
I hope this helps.