Sammy Hagar

Groupology: 
Montrose, Sammy Hagar, Van Halen
Strengths: 

Songwriting:  Sammy Hagar consistently writes strong songs.  Occasionally they might stray into the sappy, like "Love Walks In," or "Your Love Is Driving Me Crazy," but he still consistently comes up with riffs and songs that stick in your head:  "One Way To Rock," "I Can't Drive 55," "Three Lock Box," from his solo albums are great riffs and songs.  The title song from the movie "Heavy Metal" also stands the test of time.  Even when writing only lyrics for Van Halen, he comes up with memorable stuff.  The lyrics for the Montrose stuff kicked major ass.  He's an incredible singer with tons of soul.

Weaknesses: 
Inconsistency.  He only had one or two very good solo albums.  Everything since has been typical rock songs about drinking and parties.  He failed to capitalize on the huge success of 5150 and OU812. Subsequent Van Halen albums were weak in comparison.  The only person he seems able to work with on a regular basis without arguing with is Michael Anthony.
Guitar Style: 
Blues.  Very strong British Blues influence, later stuff shows that he's learned from his time with Ronnie Montrose.  Lots of pentatonics.  Some serious melody in there as well.  There are Van Halen videos where he cops EVH's style very convincingly, down to the taps.  It is possible he could pull that kind of thing off on the fly, although it is unlikely he would.  Very under-rated player.  Strong tremelo-picking ability.
Typical Gear Choices: 
Hamers, Kramer Berettas, lately, signature guitar made by Yamaha.
What You Need to Know: 
One of the greatest Dino singers ever.  Under-rated Dino guitar player as well.  A worthy 2002 inductee in the Dino Hall of Fame as a singer.  Probably not worthy of the same honor here as a guitarist, but worthy for honorable mention for sure.
Essential Recordings: 
Montrose, Paper Money, Three Lock Box, Standing Hampton, 5150, OU812