I think I'm going to use Courier New as Sergiocornaga suggests. I would make my own enlarged version of the original font, but there are many characters I'm unfamiliar with.
@ Sergiocornaga: The trouble you're having with additional characters may be due to the ASCII format the signs use. I suggest saving the World.ini in that format if possible. These are the characters that should be available:
!"#$%&'()*+,-./0123456789:;<=>?@
ABCDEFGHIJKLMNOPQRSTUVWXYZ [\]^_`
abcdefghijklmnopqrstuvwxyz
{|}~€‚ƒ„…†‡ˆ‰Š‹ŒŽ‘’“”•–—˜™š›œžŸ
¡¢£¤¥¦§¨©ª«¬®¯°±²³´µ¶·¸¹º»¼½¾¿
ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞ
ßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ
!"#$%&'()*+,-./0123456789:;<=>?@
ABCDEFGHIJKLMNOPQRSTUVWXYZ [\]^_`
abcdefghijklmnopqrstuvwxyz
{|}~€‚ƒ„…†‡ˆ‰Š‹ŒŽ‘’“”•–—˜™š›œžŸ
¡¢£¤¥¦§¨©ª«¬®¯°±²³´µ¶·¸¹º»¼½¾¿
ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞ
ßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ
Note: My browser, set to UTF-8, doesn't recognize 6 of these.
@ Headgrinder: I'm glad you like the idea. Like normal signs you will have to use the World.ini.
It will be simple though:
[x1000y1000]
Title=Myskglurgisk Grottglufs
[x1001y1000]
Subtitle=Song: Nurykabe - Arrivée distante
Progress Report: I added the Sign to the Sign dialogue. Which means, as you type your Sign text it will appear in a Sign bubble exactly as it will in the game. I don't know about you, but I waste a lot of time formatting my Sign text which required me to edit the ini, save, test level, repeat until perfect. Now, it will be one step, write text using the Sign dialogue.
Edit: 04Apr2012: Digging into the Sign font has led me to discover that I am familiar with most of the characters. They're just illegible. So, I'll be replacing the font you're familiar with with a cleaner version. For the most part I think the change will go unnoticed, but we'll finally be able to write Dr. Cliché properly. See the attachments for a comparison of old and new fonts.