Silly:
* Hunky-dory: This one is just fun to say, but means "everything is fine"
* Hairbrained: For someone with wild ideas
* Hullabaloo: A boisterous event, almost a synonym for "chaotic"
* Humorous: Well, duh! But still fun to use
* Hilarious: Similar to "humorous", but with more emphasis on the laugh-out-loud factor
Sarcastic:
* Horrendous: For something truly terrible, but you say it ironically
* Harrowing: Used for a painful or difficult experience, but with a hint of amusement
* Hasty: For someone who rushes into things without thinking
* Hideous: For something you find aesthetically offensive, but want to make light of
* Horrible: Similar to "hideous," but even more over-the-top
Odd:
* Hotheaded: For someone easily angered
* Haphazard: For something completely disorganized
* Heuristic: A word that sounds technical but is actually just a fancy way of saying "trial and error"
* Hokey: For something that's a little bit cheesy or outdated
* Hypocritical: For someone who pretends to be something they're not
Bonus!
* Humbug! A classic exclamation of disbelief or annoyance
Let me know if you'd like more!