It occurred to me that in the only instances I’ve heard the word used, it’s been to say, “wage war”. I couldn’t come up with a single other wage-able anything. This is bugging the hell out of me. It never occurred to me just how strange the word ‘war’ is.
Wage a battle ? Never heard… but doesn’t seem wrong.
Sex, conversation, sleep…
It means ‘to engage in’ by the way.
I’m gonna wage masturbation one of these days. 
Why wait?
You can definitely wage battle. Merriam-Webster’s Unabridged Dictionary (I no longer have access to the OED…=() gives ‘wage war’, ‘wage a campaign’, ‘wage a battle’, ‘wage a filibuster’, and ‘wage a fight’ in its examples. I suppose you could wage any type of military or otherwise aggressive action: ‘wage a prolonged assault’. (Except for sieges – you always lay siege.)
My mom used to have a bumper sticker that said “Wage Peace.”
You can always wage a bet
ok, a lot of those don’t sound right to me.
Is there a rule as to what constitues wage-able?
Campaigns are waged.
OED includes the following transitive usages (some quite rare and archaic):
wage love
wage a weapon (to wield)
wage works (to put out for hire)
wage workers (to employ)
wage money (to stake or wager)
wage lives (to risk the loss of)
“Wage” has been a flexible word in the course of the language, but is now sadly relegated to a rather ignominious usage.