At the beginning of the year, I refused to buy anything but the cheapest equipment, except for the stethoscope.
The stethoscope you will use all throughout your training, so it makes sense to buy something of good quality. I got the Littman III on allheart. I suppose you can get away with a toy one for the preclinical years, but I can't imagine that being a good strategy later on, when distinguishing what you hear starts mattering a lot more...
BP cuff does seem to be an exaggeration... Never heard of doctors carying these around, but if your school absolutely requires it, I guess you'll indeed need one. Find out from upper classmen! And you really can learn to take a BP measurement quite fast, it is not that complicated a technique. So --personally-- I don't think a BP cuff is worth it at all, if you can find one to learn on.
Tuning forks and pen lights you can get for really cheap, as well as the reflex hammer (like $20 for all, max. Probably a lot cheaper if you get online). So, why not?
Now the really tricky issue of oto-ophthalmoscopes. I was absolutely against getting this expensive piece of equipment given all the arguments exposed here and elsewhere. I even got through my Physical Exam class without one, just borrowing from people in my class. When I asked upper classmen, I got the whole spectrum of answers. From "don't, it's a waste of money" to "you really need it several times throughout, so you'd better get one." Finally, I've decided that if I want to really learn eye and ear exam techniques, it is really good to have my own set. Borrowing from friends makes this difficult because every model is a bit different, and so on top of the innate difficulty of these techniques (specially fundoscopy), having to get used to a new instrument everytime you have a session complicates things further.
Having said that, I'm still reluctant to throw the ~$400+ at Welch-Allyn on principle. At the moment, it is also impossible for me to come up with that money and not end up homeless during the summer... So I've been looking into the wisdom of getting a cheaper set. From experience with a number of sets (from my borrowing days), I know that the difference in quality is noticeable, but won't stop you from seeing what you need in most but the absolute cheapest of sets. That, and the fact that most doctors never carry these, have made me decide for a low to mid-range set. If I had the money, I'd probably invest in a Welch-Allyn-like set because they are really easy to use and the view is actually pretty nice. Then I'd sell it to get some of that money back. Since that is a luxury I can't afford, I spotted this little set that seems like a good fit:
http://www.amazon.com/Riester-Pen-Scope-Otoscope-Ophthalmoscope-Vacuum/dp/B0013EMTC4
From the limited reviews I've found, and from actually trying it out in the bookstore, it looks like it will do the trick. The optical quality is definitely inferior than that of the W-A stuff, but it's not as low as others my classmates have bought (ADCs and nameless brands). Also, by virtue of being cheap, I won't be as aprehensive about taking it with me on the wards in the future...
Bottom line, I think it is wise to get one. At least just to learn the basics. Hope that helps!
PS. Does anyone have any experience with the oto-ophthalmoscope set (Riester Pen-Scope) posted above? There are very few reviews online, and would like to know a bit more about it.
EDIT: So, just corresponded with a fellow here on SDN who has the above scopes. He doesn't recommend them for learning. Back to the drawing board...