What kind

I strongly recommend Full Metal Panic. It has action, humor, romance, great characters and beautiful art (well, Fumoffu's art is a little bit weak bur still... :P) If you prefer school themes go watch hilarious FMP Fumoffu, for something little more dramatic Full Metal Panic and FMP The Second Raid will do. Oh, It's based on the novel that will be released in english in US this september so check it out^^

Since you didnt mention any genre so I'll just say what's in my mind. I recommend watching Samurai 7--it's a really good one if you like.... well, blood, sword-fightings, canons.... sort of.

rurouni kenshin is a classic - full of samurai, fighting, betrayal and just a little bit of romance bleach is also good. tsubasa chronicles if your into cardcaptor sakura and/or xxxholic, was it? i'm not too sure what it was called. Naruto - i'm sure you've at least heard of this. ninja, dreams and not giving up. i would also say inuyasha except it gets boring after a while.