So I'm not an experienced hore person, I'll throw that out there first lol. I have such a passion for them, and in high school we owned and boarded three but I am very anxious when meeting new horses due to a slight bad experience I had as a child (that for some reason always made me slightly scared after that) and I spend a lot of time just hanging out in the pasture or leading, or brushing and generally hanging out with a horse before I ride them the first time. There has only been 2 horses I have a "special connection" with, where I could just jump on them anytime, do anything to them / with them. (Bareback, hugs, kisses, riding confidently) - and Lacey who I usually ride when we go out to the farm we ride at is getting up there in age and can't always be ridden for long periods at a time. I have riden more this year than I ever have, and am starting to want to go on longer trail rides and overnight camping trips with the horses out of town - but Lacey will not always be an option for that.

The farm we go out to has a handful of horses, but only a few can be ridden, so when Marion got the call that there was a horse free to a good home, she went and picked him up. This horse used to be the type the owners would throw anyone on, but one of them got very sick and doctors appoints took priority to their horses, and he and a pasture mate were let out in the field for a few years unridden but given attention. Then the draft horse they had in with him passed away and he had been alone for at least a year and they finally decided to let him go somewhere he would be loved.

His name is Charlie, he is 12 years old. The old owners said he was brown when they got him but he's greyed out and has some spots so she's thinking he's an Appy, QH mix or maybe some paint because he has 3 full white legs. Marion is hoping by next year he will be another horse I can try out, once she sees how he handles and everything. He is a LOT pushier than I have ever been used to but I'm not exactly 'scared' of him or as nervous as I usually am at first. He kind of reminds me of a big dog. He comes to you as soon as you open the gate, stands well to be hooked, but he likes to be in front when you lead him. He doesn't drag us, and stops when we stop, he's just got a lot of energy. He hates to be tied, I think he thinks when he's tied to the grooming post that we are leaving him there alone, because he stands fine when we are holding the lead rope. He's always got to check on you to see what you are doing, and doesn't seem like he has a mean bone in his body, but Marion has said he does act studdy around mares.

The main reason for my post is I'm worried if I don't constantly watch his face that he's going to bite one of us lol... that sounds terrible but he doesn't like "attack" or anything but he is ALWAYS sniffing looking for something. He's nuzzled my face, nibbled on my neck, breast through my shirt, hands, legs, grabbed and pulled on my jeans, and even once grabbed a brush out of my hand and took off and would not give it back LOL. He's been alone for so long I'm sure it's nice for him to have company now, and be playful, but I jump when he reaches his head around to nuzzle/nibble me, and it makes me nervous thinking he's going to accidentally hurt me. Is there any way to break him of this? 

You could do some natural horsemanship exercises with him. The actual problem is that he isn't aware of your personal space and he probably isn't respecting you. Also, because he's so pushy, I'd say he probably doesn't respect you either, which is a big problem and can lead to someone getting hurt if the behavior gets out of control. 

I would research natural horsemanship videos (or find a natural horsemanship trainer) that teach you to gain respect and personal space from your horse on the ground. Here's a video I found on YouTube: https://www.youtube.com/watch?v=7JQCEhNs510 (actual training starts at 1:30)

I implemented Downunder Horsemanship by Clinton Anderson to teach my horse to respect me. I watched the videos through DVD but it was about 14 years ago so I don't remember what the DVDs were called. It was a free lunge exercise that really helped teach the horse to respect me and respect my personal space (and any other person that handled him). It also helped the relationship and bonf between my horse and I when I first got him, he eventually would follow me around without a halter/leadrope. If you want me to explain the exercise, or maybe try to help you find the DVDs online, message me :)

Azalie recommended Clinton Anderson's videos to me and what i've seen on youtube already has been extremely helpful with Hunter. He is also very pushy and a bit disrespectful particularly with personal space. I highly recommend checking out Downunder Horsemanship!

I third natural horsemanship. But being a trainer for many years I can say he is attempting to bond with you via the nibbles and nudges. I follow the monty Roberts methods. And have spent many hours figguring out the launguage of Eqqus. A horses natural way to bond with another is by first a sniff to smell the other. We as humans have a different smell as hey we eat weird stuff. A horse after getting used to our smell will then start with the rubbing this is where we should say hey stop that it's out of my comfort zone. Allow a bit of touchy feelie but not too much and never show aggresion as you don't want him to be scared of you. If you've spent time in the paddock amongst a heard you most likely have seen step 3. The nibbles. Where two horses do the "you scratch my back I scratch yours" this is an amazing feat as those two horses have established their pecking order and formed a bond. This in a way is what we strive to achieve in natural horsemanship. To bond with these magnificent creatures. Look up the join me method by monty Roberts it is in my opinion the best most natural method around.

Super late to this, but I would also add to what everyone else said that you have to remember that horses are treating you like a horse. A horse that nips you on the arm or the shoulder (in a non-agressive way) is likely telling you "hey! I'm itchy on this part, can you scratch me there?". That's why sometimes you will see two horses chewing on/biting at each other in the pasture. When I had my colt, Brooks, He would nip at other horses right behind the ear, with the goal that they would the nip back and take his halter off for him.

However, on that same note, they are expecting you to treat them like a horse in return. Out in the pasture if a horse does something that another horse doesn't like, they're going to abruptly put a stop to it, either with a bite or kick out. They don't always understand scolding human-style. So, my advice for you would be to carry a crop whip with you when you groom (I stash mine in my tall boots, so it's right on my leg should I need it), and if he nips at you, give him a swift, but not overly aggressive tap on the shoulder and firmly say "NO!". For lack of a better term, you need to put him in his place and establish that you are not buddies.

Non-aggressive nipping isn't dangerous in a "I'm about to get attacked!" way, but it can still be dangerous. They are big animals and their skin is a lot tougher than ours. They don't realize that we're sensitive, haha. It doesn't take much for a small nip to become an actual wound.

As for rubbing on you, I would put a stop to that as well. It's cute and sweet, but it's not super cute and sweet when you're trying to put a bridle on or take one off. Especially because it's an easy way for a horse to knock you off your feet, and if you happen to be changing from a bridle to a halter at that moment, then the horse could have the oppourtunity to get away. Plus it's an easy way to ruin your shirt with slobber :P.

Lastly, I'm not sure what your general practice with treats is, but if you think he may be rooting around for a treat, I would set some boundaries with when and where he gets them. For example, he ONLY gets them in the grooming stall after you are completely done for the day and he is ready to be put away. And don't have them in your pockets or on you until it's time to give him one.

I hope that helps! :).

P.S. With regard to grabbing brushes and such, I don't really have any good advice to stop that, but my best guess is boredom. Similar to how some horses will start pawing the ground or doing that lip flapping thing when they get bored. If it were me, I would try to keep grooming sessions short, or to take him out and lunge for a bit in between to keep his mind busy.