Once you make it to Level 9, you can access a hidden part of the game. Simply run the file "TFFINFO.EXE" when you have a save at at least level 9. There, you can explore a small town, whose denizans give tips and information. Not that you'd really need that with this shrine, though...>_>
There are two spots where you can always go to fully restore your HP: The spot in the Tomato Patch where the game begins, and at the outhouse (gross!).
Not really a secret, but the sign in the Tomato patch that reads "Peligro! No vaya a la derecha!!" is Spanish for "Danger! Don't go to the right!!".
If you go up to the little inlet on the west side of the toxic pond, you can drink the pond water. I'd recommend against doing so, though, since it'll bring your HP down to 1.
If you search behind the silo, Tomato will vandalize the back with his name. That troublemaking little whippersnapper!
Interestingly, if you power-level yourself enough, you may be able to avoid the battle with Old Bessy altogether. Starting at Level 11, you can pass through the gate without having to use the Key. And starting at level 12, you can pass right through Old Bessy without fighting at all.
Having trouble with the Farm Spirit? You can defeat it easily by casting Deep Freeze.
Certain tombstones in the graveyard play music when you examine them. The music each tombstone plays is as follows (imagine each tombstone numbered from upper left, then right, then to the next row, like the english language):
The 1st tombstone plays "Greensleaves".
The 7th tombstone plays "Yankee Doodle".
The 12th tombstone plays "The Battle Hymn Republic".
The 6th tombstone plays "Hark! The Herald Angels Sing".