Enable the console window in the game options. Then, press ~ (or `) during game play and enter "give" at the console window.

Now type after that one of the following item to spawn the corresponding item.

w_knife.tik
w_cards.tik
w_mallet.tik
w_jackbomb.tik
w_eyestaff.tik
w_icewand.tik
w_jacks.tik
w_blunderbuss.tik
w_demondice.tik (Use multiple times to get all three Demon Dice)
w_ragebox.tik
w_watch.tik