In my review I did not go into any detail on more than one or two items, so here is a list of items that made me go, "Damn, that is awesome and I would so want that if I ever got a chance to play." I tried to avoid picking just rare/high-level stuff, but for obvious reasons they tended to have a high wow factor.
Frost Brand Weapon (level 8+ rare)
It works on any melee weapon, deals d8's on crits, and gives you fire resistance of at least 5 (scales by bonus). It has a close-blast encounter attack that deals damage and immobilizes--making it good for defenders and melee strikers--but also has a minor-action encounter that extinguishes fires in a massive burst and allows allies to make saves against ongoing fire damage. The downside is that it always deals cold damage, one of the more common resistances in the game.
Cloak of the Phoenix (level 20+ uncommon)
This is a neck item with a daily power that triggers after you are dropped; enemies within a 3 square radius take automatic fire damage, all effects on you end, and you gain hit points equal to a surge. The downside is that you lose the rest of your surges. Higher level versions restore half your hit points or all of them.
Wand of Fire (level 15+ rare)
Another one of my favorite character archetypes is a tiefling pyromancer/wizard that emphasizes fire magic. The wand of fire lets you maximize your damage dice on a fire attack once per day, and once per encounter you can both exempt all allies from the area effect of a fire attack and cause one adjacent object to catch fire.
Diamond Cincture (level 10 uncommon)
Depending on the item's level it comes with 1-3 diamonds, with an identical bonus to Fortitude. As a minor action you can spend a healing surge, causing one of the diamonds to crack and darken, which also reduces the bonus to Fortitude by one (they come back after an extended rest, though). I like this because it can basically give anyone wearing the equivalent of a dwarf's healing surge usage, and it not only takes up the waist slot (the most useless of slots, to me) but it also gives you an item bonus to Fortitude. I cannot see any defender not wanting this.
Ring of X-Ray Vision (level 25 rare)
This blast from the past gives you a bonus to Perception, prevents adjacent creatures from having concealment, and lets you see through objects; 20 feet of cloth, wood, or similar vegetable matter, 10 feet of stone, or 1 foot of metal (except for lead, gold, and platinum). You can sustain the power, but it suppresses the Perception/concealment property, unless you hit a milestone already. It is not such a big deal, because the power is an encounter one.
Guardian's Whistle (level 4 uncommon)
This low-level wondrous item lets you teleport an ally within 10 squares to any square adjacent to you. Though it can only be used once per day, this would be great for getting an ally into or out of trouble as the situation warrants.
Ebon Armor (level 3+ uncommon)
This grim-dark armor gives you necrotic resistance, but also allows you to gain temporary hit points when an enemy next to you dies. The best part? Those are both properties.
Robe of Useful Items (level 2+ common)
This magic armor can produce a generic, non-magical item of up to 10 gp in value. The power is cited as a daily, but after an hour the item vanishes and you regain the use of it. In the hands of a typical player, this basically removes the need for light sources and having to carry lots of supplies (for example, you can just conjure a rope). In the hands of a creative player? Well, then it could really shine. My only gripe is that higher level versions do not let you conjure more items.
Life-Draining Gauntlets (level 6+ rare)
I am a huge fan of necromancy, and these gauntlets provide a scaling bonus to necrotic damage and let you gain temporary hit points once per day after hitting a creature with a necrotic attack. Simple, but effective.
Potion of Cure Light Wounds (level 1 uncommon)
Formerly an adventuring staple in 3rd Edition, these finally make their appearance, giving you back 1d8 + 1 hit points at the cost of a surge. While not nearly as good as potions of healing, they are cheap at 20 gp a pop. Another good thing is that they work even if you do not have any healing surges left, but only when you are bloodied.