i can get a Ti-nSpire for about what a Ti-84 costs, and a nSpire has a snap-in keyboard and an emulator for an 84, along with a better screen. my first instinct is the nSpire, but is the emulator good? i don't want to get what i think is a kickass calc that can become the calc my class wants and end up with a buggy calc
No brainer. If you can get the Nspire for what an 84 costs, get the Nspire. I'm not saying it's completely future proof, but I'm fairly sure it's all you'll need for plenty of years to come.
http://www.studentcalculators.co.uk/acatalog/Graphical_Calculators.html (iirc they dont want any 'proof' if you want the teacher version...)