Anyway, this is a call-out to all those OCD solve-everything gamers to help me build a list to see if I'm missing anything. For example, I'll get this thread started:
WARNING: THERE ARE MAJOR SPOILERS HERE.
Portcullis killing: You can kill creatures with the portcullis, but only receive 25 exp
Easter Eggs: There are 3 easter eggs. Upon retrieving all 3, placing them in the candelabra thing in Shadowmirk will level you. For the record, sadly, I had to look up the "apple" part of that quest. I thought it was looking for the acorn, but I turned that in for the quest and I thought I may be out of luck.
Killing Lillith reward AND the sword: If you take the quest to kill Lillith from that shady guy in the Blackwater inn, go kill Lillith, then loot the repository chest her amulet opens, then give that shady guy the amulet and collect your reward. This was the coolest twist and fun way to play a quest that I've ever seen. You get the gold and the thing he wanted. I am still laughing about it.
Locked Chest in Goblin Tower: The code is 66, obtained by talking to the goblin in the Hive Queen's cave
Lever Puzzle in the Hive Queen Cave: I solved this by just treating it like 6 bits and figured there must only be 64 combinations. That was assuming that they didn't need to be turned on in any order. Was there a better way to figure this out? Anyway, then there is a chest that says open with S T E E L. I just figured out how many letters into the alphabet each letter was, then added those values together (68 I think). Then it was just gold. Kinda sad about that, I was expecting something amazing.
Gems in Hive Queen Cave: There are many gems in this cave, but you need a high Spot Hidden to see them. I've personally found a huge emerald and some diamond chips (or maybe it was emeralds). (Thanx BasiliskWrangler)
Secret Door wall in the Cemetery: There's a secret (false) door in the far south room (has 3 bats in it) in the far SE corner that leads to a lab that contains the book that the magic vendor woman (Abygale) wants in Aridell. For the record, the coolest part of this door was that I found it because an injured bat was running from me and he ran through it in an effort to escape.
Ossuary locked coffin: I can't remember the code, but when you give the acorn to the tree in Tanglewood, he will tell you the number you need. Its a locked chest that kills you if you put in the wrong code. (thanx rocketman28)
Objects I think are worthless: Chronometer, weapon fragments, femur, skull, plates and cups, ink and pen
Lighthouse: I believe this was an unfinished, or undeveloped, quest, so lighting it to get 500exp is just free XP but serves no other purpose
Skill-based Items: I think everyone knows this, but I kept a large number of items with skill bonuses (ie. Lore +6 ring and two alchemy +3 rings to name a few) and just put them on as needed. For example, I bumped Alchemy up to 9, then would just put the two Alchemy +3 rings on to craft at Alchemy 15. I would also put on my +5 meditation amulet before resting or while just exploring, then swap in my combat amulet as needed. It would be cool to have "outfits" saved and hotkeyed, so you could easily swap in different outfits as needed.
6 coffins outside Ossuary: Did these mean anything? I thought maybe they tied in to helping you figure out the 6 lever puzzle in the Hive Queen cave, but if not that, anyone find a use for them?
NPC's hate your enemies: On one occasion, I ran back 5 thugs into Bordertown and the Archery and Alchemy NPC's housed them. All you need is the killing blow to get the XP.
Enemies hate your enemies: Thugs hate slimes. I don't know if all creatures are hostile towards each other, but at one point, I had 7 slimes chasing me, and I ran into some thugs. I ran off screen and came back to find them fighting. Yet another time I mused at just how cool this game is.
Odd key: I never used this. Maybe I picked the lock it went to. Anyone know what it goes to?
See where I'm going with this? Did I miss any secret doors, etc? Let's build the ultimate list

*j