Gnawed Thumb Ring, if you use it: Have a nibble, increasing your healing and magic damage by 5% for 12 seconds. (lol wtf?)
Empowered Ring of the Kirin Tor: Use, Teleports caster to Dalaran.
Oakheart's Gnarled Root: Ranged attacks have a chance to deal additional damage over 6 seconds and reduce target movement speed by 30%.
Portable Manacracker: Critical strikes have a chance to apply Volatile Magic, at 6 stacks Volatile Magic is converted into Withering Consumption, dealing arcane damage over 12 seconds.
Emalon's Charged Core: If Crash Lightning hits 3 or more targets, you deal 10% increased damage for 10 seconds.
Of course there are set bonuses, which follow a bit of the above ideas (but within sets). And there are legendaries (iirc Legion made it easier to farm them, in that as you fail your chance to get one goes up slowly - but still quite rare lol). Also imo its awesome to have lore thematic item effects, some of them are pretty big names too. Would be like getting Louis's staff with some void time magic ability on it, pretty epic.
Like:
Roots of Shaladrassil: Standing still causes you to send deep roots into the ground, healing 3% of your max health every 1 sec.
Sephuz's Secret: Gain 10% increased movement speed and 2% Haste. Successfully applying a loss of control effect to an enemy, interrupting an enemy, or dispelling any target increases this effect to 70% increased movement speed and 25% Haste for 10 sec. This increase may occur once every 30 sec.
Prydaz, Xaveric's Magnum Opus: Every 30 sec, gain an absorb shield for 25% of your maximum health for 30 sec.
Kil'jaeden's Burning Wish: Use: Launch a vortex of destruction that seeks your current enemy. When it reaches the target, it explodes, dealing a critical strike to all enemies within 10 yds for (317030 * 200 / 100) Fire damage. (1 Min, 15 Sec Cooldown)
Norgannon's Foresight: Standing still for 6 sec grants you Foresight, allowing you to cast while moving for 4 sec. This duration begins when you start moving.
Mantle of the Master Assassin: While Stealth is active and for 6 sec after breaking Stealth, your Critical Strike chance is increased by 100%.
Cinidaria, the Symbiote: Your attacks cause an additional 30% damage to enemies above 90% health and heal you for 100% of the damage done.
Rethu's Incessant Courage: When an enemy is within 8 yards of you, you heal for 2% of your maximum health every 3 sec. When no enemies are within 8 yards of you, your movement speed is increased by 15%.
Ashbringer: Grants you the Wake of Ashes ability, which deals massive damage to enemies in an area.
Warp Slicer: Chance on hit, Increases your movement speed by 50%, and your melee attack speed by 20% for 30 sec.
Thunderfury, Blessed Blade of the Windseeker: Chance on hit: Blasts your enemy with lightning, dealing 209 Nature damage and then jumping to additional nearby enemies. Each jump reduces that victim's Nature resistance by 17. Affects 5 targets. Your primary target is also consumed by a cyclone, slowing its attack speed by 20% for 12 sec. (Sort of a goof weapon, cause it was ridiculously rare at its time, and so very people were able to use it when it wouldn't be that bad lol).
Of course not forgetting they can be fun too:
Underlight Angler (fishing rod): Grants the Undercurrent ability, allowing you to instantly teleport to the nearest fishing node within 100 yards.
Flexweave Underlay (sort of a materia): Permanently attaches a flexweave underlay to a cloak, allowing you to turn the cloak into a parachute and fall slowly for 30 sec.
Kaldorei Wind Chimes: Hold the chimes up to the wind and check the weather. (1 Min Cooldown)
Explosive Sheep: Summons an Explosive Sheep which will charge at a nearby enemy and explode for 122 to 148 damage. Lasts for 3 min or until it explodes. (1 Min Cooldown)
Although for some of the goofy items it is to note that a number are being translated into the "toy box" a place where you can collect goofy/fun things to play around with like shooting rainbows, planting flowers on the dead, summoning a gifting robot (once a day) that will gift players but fight other robots lol, dancing totem girl that turns others into a fiery dancer on interaction, remote control flying stuff, drinking kegs, group mounts (one of the cash shop mounts lets you let other players have a temporary version of it when you drop a totem down), etc, etc. (I like the group ones like everyone dancing or doing the train sound, but that quickly becomes awful in raid scenario XD). Blood orb makes you a hulk sort of:
https://www.youtube.com/watch?v=jcwZBujDrQA , big list of goofy items:
http://www.wowhead.com/forums&topic=169639.1#p2321442