You really don't want to find out

Leave me alone and I will sleep forever

Wake me up rudely and I will rock you with a jab

You will be little hard of hearing but you will thank me forever!

Who am I?

• Are any of the answers close to what you had in mind? Nov 18, 2017 at 13:44
• Yes Indeed. Just waiting a little. Couple of very surprising ones with good fit
– DrD
Nov 18, 2017 at 13:54
• Okay, the accepted answer makes more sense than mine. Lol I would, however, propose the change of "Who am I" to "What am I" given the intended answer. Nice one! Nov 19, 2017 at 20:14

Are you

an airbag?

As for the title and clues,

You really don’t want to set off your car’s airbag. An airbag will only go off in a collision (rude awakening), it will hit (jab) you hard, it makes a loud bang, and it saves your life.

• Good one. Do we really need to wake them up(in case of an emergency)? As they are supposed to be automatic. Right? Nov 18, 2017 at 14:59

It sounds like it could be a

Smoke detector (though if this is it, then other things like a carbon monoxide alarm would also fit)

Leave me alone and I will sleep forever

If no smoke appears then it will never go off

Wake me up rudely and I will rock you with a jab

When it goes off your body gets shot with a bit of adrenaline. Like a jab to your nerves

You will be little hard of hearing but you will thank me forever!

Normally the sound is loud and piercing, it hurts your ears, but it tells you that there is a fire and to get out of a building. It can save your life, so you'd thank it forever.

• It is a good fit Paige. However many times I test the smoke detectors to make sure they are working. During tests they do make noise.
– DrD
Nov 18, 2017 at 13:56
• Testing isn't really leaving it alone, is it? Nov 18, 2017 at 16:18
• Yeah. But smoke alarms don't stay quiet. When the battery runs out they start chirping. That is not sleeping forever when left alone
– DrD
Nov 18, 2017 at 19:39

Maybe this is a silly answer, but are you:

The Hulk

Explanation

Leave me alone and I will sleep forever


When Bruce Banner is not made angry or is left alone, the Hulk could stay "asleep" forever.

Wake me up rudely and I will rock you with a jab


Any time Bruce is made angry and turns into the Hulk, the Hulk usually punches the first thing he sees.

You will be little hard of hearing but you will thank me forever!


EDIT My answer is no longer applicable with the new wording but was based on the previous wording "Little hard of hearing but you will thank me forever!" And my explanation was "The Hulk doesn't really listen to orders, but he's a crucial part of the Avengers (or Thor's team in the latest movie) and is to be greatly thanked for his reckless heroism."

Who am I?


The Hulk

You really don't want to wake the Hulk up. "You wouldn't like me when I'm angry" You REALLY don't want to find out.

• Hmmm. Interesting. My answer is very different Hawkeye
– DrD
Nov 17, 2017 at 23:49
• @DEEM LOL! Yeah, I didn't think this would be it. But it seemed to fit so well. I think all the Marvel fans will appreciate my effort though. Lol. I had to try. I'll keep chewing on it. =D Nov 17, 2017 at 23:52

I think it's

Leave me alone and I will sleep forever

Well they don't do anything if they are never used

Wake me up rudely and I will rock you with a jab

If you plug them in when the volume is turned up high, they kind of give you a "jab" of a burst of sound

You will be little hard of hearing but you will thank me forever!

Earphones do make you a little hard of hearing if you use them too much but they are very helpful in life and they can be useful in many situations

It could be

Seat/safety belts of an automobile

As,

Seat/safety belts can be kept in an un-applied condition and they can lie like that forever
When brakes are applied in a speeding vehicle, seat belts come into action rudely with a small thud/impact but we thank them ever for their intended purpose.

• Hard of hearing? Nov 18, 2017 at 11:57
• Hard of hearing - can be interpreted as - they work quietly and it's hard on wearer's part to hear it clearly, perhaps:-) Nov 18, 2017 at 13:11

is it a human talking to (or about) their alarm clock?

leave me alone and I will sleep for ever

human will sleep

wake me up rudely and I will...

human turns alarm clock off when they wake up

you will be a little hard of hearing...

alarm clocks are loud but necessary