you can make the pure sine in anything. I like soundforge because, from what little I understand, It's a really clean sine. you could do it in operator, or whatever you want really.
Also, I've made decent ones in massive as well (which I then layer those 'thwomp' sounds i was talking about making) - utilizing one of the envelopes to modulate the pitch of the oscillator (which should be a sine, obviously

), with no attack and a super short decay will make a pitch drop that adds punch and attack to the kick as well. thats kind of an old trick, and if you've got something like Battery, you can do this really easily. The pitch envelope helps, and I recommend it as well.
if you do use operator, just make sure you set the carrier to fixed, and set it at 40 hz, which, by the way, is apparently the resonant frequency of the human pelvic bone.
coincidence? i think not!
I also ultra-compress the "sub" of the decaying sine wave so that it's pretty much either fully loud, or off - which allows for a nice long bass. I'll throw all of these kicks in a Sampler in Live, and then a drum rack - and assign macros to the sample selector, Kick decay (release too), and pitch. This allows for a really flexible "kick maker" rack - shit's really versatile!
I could send you some 808 kicks i've made - like all sample design, a good one takes time, and I've got about 10 i'm really happy with, but I'd be happy to send you a few examples. All the kicks in any of my 'Trap" tunes on my soundcloud (check sig) are kicks I've made from scratch - check those out to see kinda what I'm talking about.
okay I need to get off this forum and get back to a few tunes. I'm stoked to see a sound-design subforum here tho! Sound design is my real passion, so I'll try and check back here regularly and share what little knowledge i've learned from my experiences.
PM me if you want a few example kicks where I use this process. shit I could upload the pure sine for you if you want
good luck, and don't give up!