Hyouka isn't half bad, I'm normally into Slice of Life but I didn't really like it, maybe because there wasn't really any romance till the end, and the end was pretty boring to me.
Anyways, there are a bunch of good anime that are less than 25 episodes.
* = Recommended
*Durarara!! - Supernatural and mystery, little action
Baccano! - Action comedy and supernatural
*Cowboy Bebop - Sci-fi and action, kind of mecha-ish sometimes.
*Samurai Champloo - Action and adventure
*Fate/Zero - Action and fantasy, best action anime I've seen.
*Darker Than Black - It's actually around 40 episodes if you include the Gaiden and season 2 - Action, very dark, fantasy and thriller
*Phantom:Requiem for the Phantom - Action and thriller
Jormungrand - Action and if I remember correctly also thriller
*Steins;Gate - Sci-fi and thriller
Eden of the East - Somewhat romance and also mystery IMO.
*Claymore - Action fantasy and adventure
Btooom! - Action and romance
Blue Exorcist - Fantasy and action
Kuroko no Basket - Sport, even though they're playing basketball it has an action-like feel to it.
*Noragami - Fantasy and action
Guilty Crown - Fantasy and action
*Log Horizon - Strategic fantasy adventure and mystery
*Attack on Titan - Action and mystery
*No Game No Life - Comedy and fantasy
Sakurasou no Pet no Kanojo - Comedy and I think Slice of Life
They're all a variety of genres so just search them on myanimelist, I only mentioned a few aspects about the genre which it mostly revolves around.