The use of ga, ka, and wa.
I learned that "ka" is the end to a question, but I've run into sentences like, "Onamae wa?". It's a question, but it doesn't end in "ka". What is the correct use of "ga", "ka", and "wa"?

Question

Answer

Sometimes you can omit 'ka' provided you use intonation to let people know it's a question. So, 'Onamae wa?' would be roughly the Japanese equivalent of 'And your name is?'. 
 
 As for the difference between 'ga' and 'ka,' I think this article explains it pretty well: http://www.guidetojapanese.org/blog/2005/02/05/the-difference-between-and/ 
 Hope this helps!

Answer

Hello again!

I'll show you some examples.

First of all, about か（ka）. For example, "Anata no namae/onamae wa nandesu ka.(What's your name?/ Can I have your name?)." "Onamae" is more formal as a question. But you can't say " Watashi no onamae wa Caitlyn.". ” Kare wa sensei desu ka.(Is he a teacher?)" "Ima nanji desu ka.(What time is it?)". "Anata wa doubutsu ga suki desu ka.(Do you like fruits?)".

Secondly, about "は(wa) ". Ex. You know, we read it as "ha" with the only one letter. But we read it as "ha" after a subject. "Watashi no namae wa Hanako desu./ Watashi wa Hanako desu.(My name is Hanako./ Watashi wa Hanako desu.)." "Iie, kare wa sensei ja/dewa arimasen.". "Dewa" is more formal. "Ima wa kuji gojyuppun desu.(It's nine fifty now.)". "Hai, watashi wa doubutsu ga daisuki desu.(I love animals.)".

At last, abuot "が(ga)". We use "が" when we'd like to emphasize something. Ex. "Watashi ga Hanako Tanaka desu.(I'm Hanako Tanaka.)" I'll say with "が" if there're some people are named "Hanako". "Kare ga anata no isha desu."(He's your doctor). I'll introduce you your doctor if there're some doctors there. "Watashi wa tokuni inu ga suku desu.(Especially I like dogs.)" I hope my explanation help you ^^

See you,
Hanako

Answer

I think that "Onamae wa?" means "Onamae wa nandesuka?" and here "nandesuka" is omitted.
It would be the same as "Your name?" in English.
Especially in a spoken language (and mostly in a casual way), we also say like:
  Ko-hi- wa? (Ko-hi- wo nomimasuka?)
  Gakusei? (Anata wa gakusei desuka?)
  Daijoubu? (Daijoubu desuka?)
  Tsukareta? (Tsukaremashitaka?)
and so on.

These may be somewhat(extremely?) confusing.
Good luck!

Answer

"Onamae wa?" is a short form of " "Onamae wa nani desu ka?". The speaker is assuming that the omitted part is naturally understood from the context. I think omissions like this can also be found in English as YagamiRaito suggested. For example, "You are....?"

The difference between 'ga' and 'ka is very difficult even for native-born Japanese. I am not able to explain it here.