The Covenant's answer - to coin a cliche - to the pistol. Turn your nose up at it if you like, but do so at your peril - you're inviting to have your proboscis ventilated in short order.
The most notable feature of a generally fine weapon is the secondary attack, or charged shot. Hold down the fire to pack in some extra punch to your plasma - and WHAT a punch it is. The charged plasma pistol shot is arguably the most devastating attack in the game. 400% shields, you say? One zap from one of these glowing globs, and he's walking naked. This has all sorts of fun implications, which you can explore on your own, but one thing's for sure: when charging down an enemy-ridden Truth and Reconciliation or Longest, you will be damned glad that you've got it. Fun Bonus Fact: The charged bolts, in addition to packing the brawn of a nuke, come equipped with a fair degree of homing. Icing on the cake - though it should be noted that tracking a vehicle, it will not.
The friendly Covenant armorers didn't stop there, however - the plasma pistol also has a first-rate ordinary fire. While not in the same league as the demon-slaying charged shot, a rapid hail of single nips is enough to ruin anyone's day. Plus, like the plasma rifle, the primary fire will stun an opponent. And the melee attack is one of the fastest in the game - consider a charged shot to drop shields, then slap the target with your melee, thus prompting much jeering and snarls.
Pros: Ruiningly powerful (and homing) charged blast, relatively powerful and quick (and stunning) ordinary shot, very fast melee attack.
Cons: Usual plasma weapon problems - i.e. inability to reload.
Usage: An entire arsenal of other weapons are multiplied in power and effectiveness when used in tandem with the plasma pistol. Plus, when simply desperate (or feeling brutal), a charged shot can solve many of life's problems. Also great to carry as a melee weapon.
For: Nearly anyone who likes quick, lethal kills. Not the most finesse-ful weapon in the game, but pragmatists, of course, scoff scornfully at such meanderings.