Even though I'm a giallo man at heart, I do love my slashers too...
Classic faves include: Bay of Blood - the DEFINITIVE slasher film, and Bava seniors masterpiece IMO.
Black Christmas - Probably my favourite slasher, has all the elements I like plus is pretty damn creepy too.
The Burning - The first slasher I ever saw (I think I was about 8 or 9 at the time) and I've been hooked ever since!
Halloween - Even though I can't stand Jamie Lee Curtis, I can't fault Carpenter's Halloween - the suspense, the spray painted William Shatner mask, the score... Perfect.
Maniac - Without Spinell, this would have probably been garbage but what a performance - he made that film.
Then of course there is Fulci's
New York Ripper - if you consider that a slasher.
More (controversial 
) faves of mine are: American Psycho - One of the best modern slashers, with a great performance from Bale.
Blue Eyes of the Broken Doll - sort of a Spanish Giallo with Paul Naschy. About a serial killer who slaughters women and removes their eyes... one of my fave Spanish slasher flicks... not that there are many!
Cradle of Fear - The whole goth n' gore thing appeals to me... that and a naked Emily Booth...
Home Sick - I don't know why this appeals so much to me as it is brainless, but it has some good gore plus a very memorable performance by Bill Moseley slicing himself up with razorblades.
Pieces - Great, cheesy fun.
Stagefright - The bad dubbing, the owl, the chainsaw deaths, the chilling tableaux of arranged dead bodies as the climax is reached... it's almost poetic... great stuff from Soavi, who is criminally underated IMO.
Honorable mention:
Family (John Landis) Master's of Horror series - George Wendt from Cheers kills people off in order to create a 'family' who are real and alive in his head.
So bad it's good mention:
Blood Feast H G Lewis' tale of the Egyptian Cannibal Caterer - what's not to like?!
I'm not a great fan of the modern slasher nor the heavy franchise slasher's such as the Friday's and The Elm Street's. The only new stand-alone slasher I've seen recently that I thought had any merit was probably
Laid to Rest - and even that I thought ended badly. I quite enjoyed Zombie's Halloween though, and I am looking forward to the sequel.