These answers are right. But, as with everything written, it depends on the context.
Simply put, wake is a verb - for now. It's not a noun in the way you want to use it. There's no such thing as a waker (as in a person), unless you found it in some royal court or something. Seriously, someone probably did have to wake up His/Her Highness. That person probably had a title. Hmmm, Lord of the Awakening?We have examples of that now. The verb marry has noun forms that are titles: priest, justice of the peace, rabbi, etc. However, there is no "marrier". It's not hard to make the conversion from wake to waker. Most English verbs have a noun counterpart. Think jog/jogger, sleep/sleeper, and kill/killer.
You can look up the accepted noun use. It's a dead person's remembrance party before burial and the turbulence caused by ships and airplanes as they traverse their routes.
However, don't count "waker" out just yet. A quick look at the OED shows that "misconstructor" was added in 2002.
Back to context... if you're writing a poem or a song then you have poetic license. Again, a quick search for "poem containing the word 'Waker'" brings up Sir Thomas Wyatt using it. There's also some song on YouTube that uses it as its title to refer to a person.
Bottom line though, I wouldn't try using it in Scrabble.
Forgot to ask, are you in the U.K.? "Waker", spoken, is dangerously close to "wanker" - British slang for jerkin' off.