Least InvocationsBaleful Utterance: Unlimited
Shatters as the spell. very very very useful.
Beguiling Influance: Will see the most use in Warlocks that want to make good negotiator. The use is limited because Diplomacy is not a class skill for Warlocks, sadly. If you add levels of a social class (Rogue, Bard) the usefulness of this Invocation increases.
Breath of the Night: I've not found a use for this Invocation yet. Fog Cloud can be a handy spell, but one that can be more easily duplicated with a magic item.
Dark One's Own Luck: A luck bonus to your saves based on your Charisma for 24 hours, but limited by your class level. It cant be used on more than 1 save at a time. That makes me less than excited about it.
DarknessThe 3.5 version of Darkness is pretty crappy. If you used the 3.0 version.. yeah, go for it.
Devil's Sight: When the Warlock was first introduced, there was alot of excitement about this combined with Darkness, but it turns out that it isnt all it's cracked up to be. There are better things to use your Invocation slots on.
Earthen Grasp: Since the spell sucks, I think this invocation sucks too.
Entropic Warding: This Invocation is so good, I dont know what else to say. 20% miss chance from ranged attacks, leaving no trail, cant be tracked by scent? Wow.
Leaps and Bounds: Might be good for multi-class Warlocks that get those skills on their list. Rogue and Monks come to mind immediately.
Miasmic Cloud: Easy to catch your allies inside, easily dispirsed. Might make a good low level Invocation to swap out later
See the Unseen: One of the best of the Least Invocations. 24 hour See Invisibility -and- Darkvision. I'll take two, and an order of fries.
Spiderwalk: A great power for those Warlocks seeking to enhance their mobility options, esp. in caves, buildings, and cities.
Summon Swarm: A decent low level power, the duration prevents you from summoning 400 Swarms.
Lesser InvocationsCharm: Another solid invocation, this one can give you a temporary cohort. Can also be used to qualify for the Mindbender PrC
Curse of Dispair: Not all that useful, since you need to be close enough to touch the target, but given that Bestow Curse can be a powerful ability, I say it depends on your Warlock-style.
The Dead Walk: If you use the black onyx you can create an undead army in a day. Even without the onyx, it is a good ability to make a quick zombie in the middle of combat. If you take Utterdark Blast, you can heal your undead minions. With Eldritch Chain you can heal mutiple targets. With Eldritch Cone you can heal your undead while affecting your enemies.
Fell Flight The crown jewel of Warlock mobility, the spell can give you flight you can turn on and off all day long. Awesome invocation
Flee the Scene: Another awesome mobility invocation. A good way to create confusion among your enemies. Too bad the range was shortened so much.
Hungry Darkness: I'm not sure what the use of this Invocation is. It only lasts if you concentrate, and it's only Darkness with a bat swarm. Seems useless.
Stony Grasp: Just as useless as Earthen Grasp.
Void Sense: Blindsense is a good ability, but I am not sure I would use an Invocation slot on it. Good candidate for the Extra Invocation feat.
Voracious Dispelling: Good Invocation. with a high spell craft, and a readied action, this Invocation could make a Warlock a good counterspeller. Note that the effectiveness decreases as your increase with level, much like the effectiveness of Dispel Magic diminishes.
Walk Unseen: I love this Invocation, but I never seen to have enough slots to take it. Who doesnt want Invisibility at will?
Wall of Gloom: Not a very useful Wall Invocation, and there are much much better ones at this level you can take.
Greater InvocationsChilling Tentacles: Awesome, awesome Invocation! This is one of the reasons Warlocks make such good battlefield controllers! Even if someone isnt grappled, they still take cold damage.
Devour Magic: I actully find this Invocation less useful than it's lower counterpart, since it can only be used as a targeted dispel, and as a touch spell. Flexability is just something a Warlock cant give up.
Enervating Shadow: A decent Invocation, but one that requires close proximity again. The Str penalty is nice, but there are better places to spend a Greater Invocation.
Tenacious Plague: A good swarn summoning spell, if that is your thing. The DC boost, and ability to treat the swarm as magical weapons for overcoming DR is pretty good. The number of swarms you summon can be pretty sick too.
Wall of Perilous Flame: Another good battlefield control spell, made even better since half of the damage is not fire damage anymore.
Warlock's call: Uh. Sending isnt that useful anyway, plus it can damage you. Sheer crap.
Dark InvocationsDark Discorporation: Why, oh why, would you take this? You can only take move actions! Blah! It basically negates your abilities to use Invocations at all. I'd rather not. I've been informed some people prefer this Invocation. Just goes to show you cant take -1- persons opinion as fact. There are instances where Swarm Traits and Immunites will be very useful, and the damage isnt half bad. I prefer to have access to my Invocations and Eldritch Blast.
Dark Foresight: Eh, I wouldnt take it. I've never found Foresight to be all that useful. The Telepathy picks up some of the slack, and is very useful for with the Charm use.
Path of Shadow: The only long range teleportation spell a Warlock gets, and it appears you can take your party along with you. Nice ability.
Retributive Invisibility: Greater Invisibility at will, and it can damage everything around you if it is dispelled. Pretty good
Word of Changing: Probably the most hiliarious ability the Warlock gets, the ability to permanently Baleful Polymorph an enemy is usually too much for me to pass up.