Trisword: It's like a DIY orc kit. Obvious combos are halfling priest, gnome warlord, or a thief of either race. It's also a good shop pickup for Rogues and Berserkers.
Martyr Wraps: Put it on a Monk or maybe a Paladin and be amazed. Play an orc monk with Taurog with this and you will swear you are playing some kind of rigged debug mode.
Crystal Ball: Too expensive to buy, but amazing as a prep. The best magic support item in the game. It's the kind of thing that you want to locker and veto at the same time.
Fireheart: The only health stacking support item in the game. It lets you do novel things with dwarves, and is interesting with Bloodmages.
Whuurgl (or whatever): A toned down martyr wrap with less power but less complication. Surprisingly good on Wizards.
Smuggler's Den: Handy for Assassins, Warlords, Monks, or other classes that need last minute exploration. The intended effect (gathering low level monsters for you to fight in the beginning) is an artifact of a time when no one really knew how to play the game.
Patches: Best if your class has a way of shrugging off either poison or mana burn. Paladins can ignore poison, Berserkers can sometimes shrug off mana burn, and Crusaders should never take anything else from the Thieves Guild. Halflings and gnomes can power through poison and mana burn respectively, and if you also prepped trisword you'll only be burning potions that you would have been wanted to burn anyway. If your class is highly mana dependent (eg warlord) consider prepping Soul Orb also.
More glyphs: Great synergy with Taurog, Mystera, and Glowing Guardian.
Less glyphs: If you are playing an orc, you want this. When prepping Taurog as an orc, I prefer this to More Glyphs.
Bearmace: Mostly good for mazes, but everyone should try out the SMASH strategy at least once:viewtopic.php?f=3&t=2050&p=17323&hilit=SMASHING+SMASH+SMASH+SMASH+SMASH+SMASH#p17323