My fondest memory of Arcanum is when I made a half-ogre with that one background that gives you like +6 strength at the cost of most of your intelligence (the one where your character ran away to join the circus?), named him Smashkill McDumbfuck or somesuch, and proceeded to murder everyone the moment I had a decent weapon and whatever large-sized armor I could find (half-ogres pretty much got shafted in the armor department, which kind of goes against their supposed character type of "big dumb bruiser tank." Then again, nobody ever accused Arcanum of being well-balanced). I think I got up to Caladon before I got bored with my killing spree.
My least fond moment was when I was playing a spellcaster, bought the "Spatial Distortion" spell (or whatever it was called, it was the 4th spell in whatever discipline Teleportation was in), and promptly discovered it was useless. The idea is that you can instantly warp from where you are to another point in the area - except in order for it to work, there can't be any obstructions (including enemies) between there and here, and you can't use it to, say, cross over streams or such. In other words, you can only warp to a spot that you're capable of walking to in a straight line. And it costs mana (or magicka or whatever they called it) to do so. The only real use for it I can think of is warping away like a scared magic bunny, and if things have gotten that bad you'll probably just reload instead. The only real reason to buy the spell is that you have to in order to buy Teleportation, which is actually useful (warp to anywhere on the world map you've already been).