People sometimes say 'heck!' when they are slightly irritated or surprised.
[informal, feelings]
Heck, if you don't like it, don't vote for him.
Oh, heck. What can I write about?
a heck of sth
People use a heck of to emphasize how big something is or how much of it there is.
[informal, emphasis]
They're spending a heck of a lot of money.
The truth is, I'm in one heck of a mess.
a heck of a saving