ah i think ive stunbled upon a unique Frage maybe. name three animes Du HAVE to watch dubbed, and three Du HAVE to watch subbed.

3 Anime ive watched dubbed are:
Lucky Star
Soul Eater
FMA

3 Anime ive watched subbed are:
The World God Only Knows
Fairy Tail
Durarara

Hmm, nice question.

My 3 I HAVE to watched subbed:
1. K-ON!
2. Hell Girl
3. Vampire Knight

My 3 I HAVE to watched dubbed:
1. pfirsich Girl
2. Death Note
3. Ouran High School Host Club

:D

Dubbed:
Pokemon
Hetalia
InuYasha

Subbed (I'm only Schreiben the ones that also have a dubb):

OHSHC
Tokyo Mew Mew
Shinryaku! Ika Musume!

Dubbed
-Any anime
-Any anime
-Any anime

Subbed
-None
-None
-None

... and for good reason, too.

An honorable mention goes to the Marvel Anime project.

Dubbed: Death Note, Soul Eater, Hetalia
Subbed: CardCaptor Sakura, Tokyo Mew Mew, FullMoon wo Sagashite

Hmmm that's a tuff one.
Fullmetal Alchemist is really the only one that has GOOD dub (especially Vic)
Oh! then there's Fruits Basket (I Liebe her cute little voice XD)
But that's it really. Everything else HAS to be subbed. It seems like Americans just scrounge up anyone to quickly dub an Anime and get done with it. Their voice Schauspielen is TERIBLE. Not to mention it takes away what the character is actually saying,and the way they're saying it.
A Japanese voice actor could be like:
"I-t-t-t-tai!"
english:
"ouch ouch ouuuuuch -_-"
just doesn't work >.>
Oh dear it looks like I've ranted on dubs once again X)

Dubbed:
Full Metal Alchemist
Soul Eater
Black Butler (british accents xD)

Subbed:
Fairy Tail
D Gray Man
Maid Sama