This kanji has to be high on the list of most underrated kanji. This is one of the ones that you learn early on (due to the fact that it’s in the word for number – 番号) but never fully appreciate until you get to the intermediate/advanced stages of study. That’s the point where you start to hear ごう interspersed throughout all different sorts of conversations.
For example, I have very vivid memories of the feeling I had when someone first said to me, 「よんじゅうきゅうごうせんにのって、ひがしへいって．．．」I give it to you in hiragana so that you can experience it as I did. “ごう?” I remember thinking to myself and then it came to me, 「４９号線に乗って、東へ行って．．．」It was marking the road number.
Being able to use this kanji appropriately will make you sound much more natural in Japanese. People would understand you if you said just 49, the number of the highway that runs East to West from Iwaki to Niigata, but it’s far more natural to add 号線.
Here are some more useful compounds:
〜（番）号室 Room number (I believe the 番 is optional)
〜号棟 Building number (one of several buildings)
〜号車 Car number (of a train – check your next shinkansen ticket and you’ll see this)
〜号 Used for names of ships (e.g. the Titanic – タイタニック号 – or the Colombia space shuttle – コロンビア号)
００７号 Special Agent double oh seven
号外 Special edition of a newspaper (literally “outside the standard count”)
称号（しょうごう）degree, as in BA (文学士の) or BS (理学士の), which seem to be shortened to 学士号 frequently
This is also one of the very first kanji I made a mental image for to help me remember it. Allow me to show off my Photoshop skills:
Give it a hat.
Then a jaw.
A crazy eyeball.
And some flecks of spit and, voila, you have yourself a drill sergeant.
“MOVE YOU FUCKING MAGGOTS! GO! GO! GO! GO!”
And now you will never forget that this kanji is pronounced ごう.