has made the most impact (musically) in your life? (although there might be lot......name only ONE and why).
 
For me, it was when I was in junior high/going into high school and heard VH 1 (Eruption). One of my uncles (an old school jazz fan) said it was all electronics (trying to discourage me in listening to rock), and gently tried to steer me in another musical direction. Of course, I made that a personal challenge to learn most of VH1 and played it for him on my cheapo Hondo destroyer the very next summer he visited.......
 
That CD was a game changer for me.

For the most impact and inspiration when I was starting out playing guitar, I would say the late Stuart Adamson (Skids/Big Country). He had the knack of popping guitar 'hooks' into a song, often palm-muted riffs like the vid below.
 
https://www.youtube.com/watch?v=9udxbvHiqGw
 
I've always strived to come up with guitar parts that 'serve the song' rather than just draw attention to themselves, if that makes sense.

Steve Russell and John England from University.  We lived together, got drunk together, got wrecked together, tripped balls together...but they were the guys who taught me to play the guitar, or at the very least (as I'm still trying to learn) put me on the path.

Their souls had been sent to the future from the 50's as they were complete rockabilly / Sun records nuts.  Both had more musical talent in one finger than I have in my entire body.  Steve could sing (best voice I've ever heard first hand, like Elvis good), play double bass and guitar.  John was one of the best natural guitarists I've ever known or heard.

Without those two guys' influence, I'd probably never have tried to pick up the instrument.

Has to be Deep Purple for me.
 
I listened to and experimented with a lot of styles in the late 70's early 80's but a compilation album I bought when I was 8 or 9 (because it had a Beatles track on it) (and I liked the picture on the sleeve) included Black Night and I've been a rock chic* ever since..
 
 
 
*ok,  maybe more of an old hen now..

Pink Floyd for me.  7th grade art class.    Up to this point music was a casual thing for me.  Something for the background rather than something to get focused attention.  The teacher gave us our assignment to draw or paint or whatever, then put the new DSOM album on while we did our assignment.  That instantly changed the way I thought about and listened to music, and kindled my desire to make music.

Igor Fyodorovich Stravinsky: Oedipus Rex

Miles Davis
 
I was raised (in the south) on classical and church music, and was fortunate enough to study piano for 3 years with the soloist for the St. Louis Philharmonic (Joanna Lange; two left-hand-only vids of her below) when I was 10-12.
 
I moved to Wisconsin at 13. The next summer (1965), I saw a documentary on the Chicago PBS station on blues music (of which I'd never heard). The first half hour was Mississippi John Hurt, sitting alone on stage, playing a resonator. [I had fallen in love with the delta blues, St. Louis style, when I'd sneak out at night and head down to Gaslight Square, grab a slice and a coke for $0.25, and sit on an outdoor bench, listening to the live bands.] The second half hour was a 17-year old Buddy Guy, playing his lightning-fast electric blues. Now I'm serious in love with the blues.
 
Fast-forward 4 months to Christmas-time, 1965. We were doing Xmas at a relative's home in Chicago. I was over 5'9" when I was 12, and never had much trouble passing for older. I really, REALLY, wanted to hear some live Chicago blues, so I snuck out of the house, took the train downtown and walked up to Old Town to look for a blues bar. Being winter, there were no open doors or windows (like I was used to in St. Louis). I saw one club that had a line of peeps, waiting to get in. Must be the best blues band, tonight, I figured, so I got in line. No problem getting in. I found a spot in a dark corner and waited for the blues.
 
Well, I got the blues...but not the kind of blues I expected. Not at all. Playing that night were:
 
Trumpet: Miles Davis
Tenor Sax: Wayne Shorter
Piano: Herbie Hancock
Bass: Ron Carter
Drums: Tony Williams
 
Oh, and the name of the club?
 
The Plugged Nickel
 
My life changed. I've never had a better musical orgasm than I had that night.
 
Edit: Here are the two videos.
 

Wow......that Joanna Lange is very impressive for just one hand!!
 
(I can't even do 1/2 of that with two hands.....) 

One Band: The Beatles
One Musician: Jack Bruce
(sea watt eye didare?)
 

The Beatles