Connect to a multiplayer game and have one player give all items to the second player. The player that gave away the items will then want to restart the game without saving. All of the items will still be in player one's inventory.
Enchant a piece of armor that gives strength to you or get a piece of jewelry that does the same thing. When you come across items you do not have enough encumbrence for, equip the strength accessory or armor, take the item, then swap the strength-augmenting accessory for your original equipment.
Remote Boss Killer
Play as an alchemist with chain lightning in your repertoire, you can kill most bosses without even entering the room. When a boss' room is not attached to the room you are currently in, but is diagonally opposite from the room you're in, you can move towards the boss icon and cause the boss' name to appear on the screen. Unleashing chain lightning towards the boss at this point will damage the boss and your whack job will be made that much easier.