These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crowning Music of Awesome: Divine Divinity is not at all short of brilliant, atmospheric music. Havealisten. Best of all, the entire soundtrack is available for free download off the composer, Kirill Pokrovsky's website.
Disappointing Last Level: Could be averted if you enjoy slaughtering literally thousands of almost harmless Mooks with your rapidly increasing powers in the final hours of the game. The exploring and questing is mostly over tough.
Game Breaker: Any weapon with the freeze attribute. It freezes people, wolves, ghosts, demons and the Big Bad all the same.
Good Bad Bugs: The "portable" bed in the house north of the Cursed Abbey (also possible by combining two straw bales in your inventory).
Also the Polymorph spell, which turns the target into a harmless critter. While it is supposed to last only a few seconds, a bug ensures it is permanent. Boss fights just got a lot easier.
You could also rob merchants blind with pickpocketting and a bit of running around. And there were dozens of ways to screw around using the Teleporter Pyramids. Including a way to avoid a moment of Lost Forever to gain the Dragon Shield.
Enemies flinch when they take damage. The lightning spell can be cast as quickly as you can click your mouse, if you've got the mana. Combine these two things and you've got a spell that paralyzes an enemy while you shock them over and over again, Emperor Palpatine-style.
Infinite money is possible by having the same item twice (preferably an expensive gem) and selling it to a Merchant. When the amount dialogue pops up, just type in "-1" and press Enter. You will have the item once more in your inventory and 255 are placed on the desk (thus you can buy anything and have change to spare). Secondary benefit being that traders will instantly like you a lot more.
Scrappy Level: Part of the plot requires that you become young Duke Janus' champion and personal bodyguard for a while. He proceeds to order you around like a servant, and acts increasingly rude and threatening if you make any sign of resistance. You're not allowed to leave, your teleportation stones are confiscated so that you can't warp away, and you're not allowed to make any hostile actions to anyone (read: Duke Janus) in the castle, no matter how justified you think that might be.
That One Level: Iona's Dungeon is one of the must frustrating dungeons in RPG history.
Vindicated by Cable: Cheap digital re-releases and frequent sales on Steam and GOG.com have helped this happen.