Hexblade

A Hexblade is an arcane class in Dungeons & Dragons. In 3e he is more or less a Spellsword with curses, an awesome attack bonus (+1 per level sweet fuck) and will saves, does not need to prepare his magic and has a big hit die. The downside to this is that, as a caster, he cannot wear anything bigger than light armor, can only have a few spells to choose from (even less than a sorcerer!), his other saves suck dick and cannot be good (becoming so results in the loss of all your powers and your familiar). He will also need a combination of Charisma (for his spells), Strength (for his attacks), Dexterity (to not die) and Constitution (also to not die), leading to heavy MAD.

You will be best served by taking spells that increase your own fighting abilities and survivability through not getting hit: by picking your spells wisely you can fill up a few niches as they up, from flanking an enemy and serving as the rear guard to punishing enemy casters. Do note that the class is not considered to be very good, because while the Hexblade can fill certain openings as they fall he cannot fill them as good as someone fit for that job can.

In 4e they work differently. Like a Warlock a Hexblade has forged a pact with powerful entities like the Fey or Fiends, but instead of getting PHENOMINAL COSMIC POWAH he gets a sword instead. Most of the time the Hexblade's patron gives this so that it can be used to shed blood/souls of the unbelievers for the glory of the blood god Hexblade's patron. They use their sword in one hand and an implement in the other, making for an offense-oriented character. As above, they require a combination of Charisma, Strength, Dexterity and Constitution to work, making them still MAD acrosss editions.