[antognini]

The really weird letter in Esperanto is ĥ. It uses a sound that isn't very common in many languages so it's hard for a lot of speakers to pronounce. (It's like a "ch" sound in German.) Typographically it looks weird. There has been a general trend towards replacing it with a "k".

[plumeria]

To me it sounds like a Spanish j. For example, ĥodiau (today) sounds to me as jodiau.

[flipcoder]

Today is "hodiaŭ". It uses the regular h.

Ĥ/ĥ is less common in esperanto and in some cases has been replaced with other letters.

[plumeria]

You are right, I mixed the accents. Interesting, will lookup some words with ĥ.