| Title | Publisher | Year | Language | Documents |
|---|---|---|---|---|
| Obscene Quest of Dr. Aardvarkbarf, The | Gary Roggin | 1997 | English | Solution |
| Off the Trolley | Krisztian Kaldi | 2005 | English | Solution |
| On the Farm | Lenny Pitts | 1999 | English | Solution |
| Once and Future | Cascade Mountain Publishing | 1998 | English | Solution |
| One Foot Down | Jason Reigstad | 1999 | English | Solution |
| One That Got Away, The | Leon Lin | 1995 | English | Solution |
| One Week | Papillon | 2001 | English | |
| Only Possible Prom Dress, The | Jim Aikin | 2022 | English | Map |
| Oracle, The | Brandon Allen | 2002 | English | Solution |