StageFright: Aquarius (1987) - is a keeper
The House on Sorority Row (1983) - was a pleasant surprise for me after watching so much guff.
Superstition (1982) Isn't strictly a slasher, but it's easily one of my all time fav 80's horror, a body count movie with (a black) heart!
Tourist Trap (1979) - Sort of
Carrie meets The Texas Chainsaw Massacre - very underrated!
Curtains (1983) - While it has a made for TV murder mystery feel to it, there's at least 2 classic scenes, real stuff of nightmares.
Terror Train (1980) - Pretty entertaining slasher flick, due to killer's costume changes!
Alice, Sweet Alice (1976) A.K.A Communion - Often gets labeled "An American Giallo", but slasher fans can still "enjoy" it.
Intruder (1989) Delivers the wet stuff and is fun with it.
Happy Birthday to Me (1981) - The longest slasher film ever, has almost soap like
qualites at times, but it ticks all the right boxes.
The Prowler (1981) While it drags for me at times, I'd still say it's one of the best 80's slashers.
Madman (1982) - A mixed bag, (Some cheese and low budget hurts it) but the atmosphere and the Madman of the title is very memorable.
Hell Night (1981) - Low body count, but it's surprisingly suspenseful towards the end.
Rituals (1977) - My favourite "Deliverance" clone, captures the feeling of
being lost in the middle of no where more so than the more known "Just Before Dawn" for my money.
Silent Night, Bloody Night (1974) - More in line with Black Christmas, I found it be a surprisingly creepy, sombre movie.
Unhinged (1982) - Often Panned, for good reasons, as not a lot happens for much of it's running time, but the ending is worth the wait!
Final Exam (1981) - A bloodless slasher, what's the point eh? I actually liked this one, pretty creepy atmosphere and I like there's hardly any motive given for the murders.
Two useful sites:
Hysteria Lives! (The reviews are fun reads)
Retro Slashers (Deals with even the most obscure stuff)