I’m looking for licks that totally define the song. Examples:
Life in the Fast Lane (Eagles)
Oh Well (Fleetwood Mac)
What others can you give me?
Damn - Oh Well is my go to for checking out the bass response on guitars.
Let me think about this.
Whole Lotta Love
Sin City
Peter Gunn theme
Who do you Love
Mannish Boy
Train Kept a Rollin
Same Old Song and Dance
How did I know you’d be the first one in? 
Thanks!
Mancini wrote for horns. P.G. is in F, a much more trumpet-ish key. It’s not in E. Not that anyone would notice but you & me.
And stop the rhyming, I mean it!
The Beatles’ “Day Tripper”
Dust My Broom
Interstellar Overdrive
Good Times Bad Times (definitive, but barely a riff)
Communication Breakdown
[Place holder for more Zep…]
Jean Genie/Block Buster
Roadhouse Blues
Planet Claire 
Rocky Mountain High is in E and a distinctive intro lick.
NoCoolUserName - this is basically the same riff as the Peter Gunn theme. In E.
Either way, fun riff to start new players off on one string.
I play Superstitious in E - Stevie Wonder wrote it for Jeff Beck, then recorded his own version. Beck plays it in E and it’s fun.
Purple Haze
Hey Joe
Satisfaction
The Spirit of Radio
If that’s not a distinctive riff I don’t know what is.
Since I don’t play, I have to take a stab at this by ear:
Are “Life in the Fast Lane” (The Eagles) and “I Love Rock & Roll” (Joan Jett) in E?
I tip my hat to you, sir.
A truly badass song by the best in the business. I love all three Blues Kings, but Freddie is my favorite.
(Note: this is the song Clapton covered on the John Mayall & the Bluesbreakers album that led to the Clapton is God graffiti. Fun, but King could blow Clapton away. Nobody liked playing with Freddie King when he was in full gunslinger mode.)
Back in Black
:smack:
One of the basic food groups! Gotta know that riff.
Small Clanger is handling Zep, but Black Dog certainly stands out as a song-defining riff. [scratch that: I am playing it in my head and realize it is in A. Rats.]
Another off-time riff song in E is Spoonman by Soundgarden. Only in 7/8 vs. 15/16 for Black Dog, but fun.
A riff that is not very well known or viewed as a big-deal Classic Rock riff but which I love is Wrong to Love You, by Chris Isaak: https://www.youtube.com/watch?v=mGoohR2bQUE I play this riff way too much to work on my fingerstyle technique.
Oh, and: Metallica - Sad But True and Enter Sandman. Sad but True is a wonderful, durable riff.
By the way: some of these are in the key of E minor. My assumption is that you want cool riffs that pivot off the Low E string and aren’t focused on major/minor.
Interstate Love Song by Stone Temple Pilots is in E and has a pretty memorable guitar hook.
Walk This Way by Aerosmith.
Barracuda by Heart.
I’m surprised nobody has mentioned “Back In Black” yet.
(post #14)
Thanks…I like Freddie the best too. I had “Freddie King In Concert” (Vestapol) on VHS that I found in a record store in Chicago years ago - wore that tape out!
If there’s a fourth “King” to be handed out though, it belongs to Earl King - born Earl Silas Johnson - underrated guitarist from NOLA.