"Full Metal Alchemist" or "Dragon Ball Z" if you want a shounen anime, if you want Mecha i'd suggest "Eureka seveN" or "Gundam Seed" and if you want drama i'd go with "Monster"

FMA took about 10 espisode around for me to get interested in it, but then it gets very good.
DBZ seems sorta predictable at times and not to many people die, but its very entertaining.
Eureka seveN is a little werid, but extremely good imo.
Gundam Seed starts off slow but gets good later on.
And Monster is only good if you like drama.

Im pretty new to anime myself, so I havn't watched a lot yet, but out of the ones I have I'd defently recommend those.