I have a Casio FX-300ES that's lasted me all the way from middle school through college-level calculus. It's pretty much invincible, though I have currently misplaced it.
I had a Casio FX-9750GII, but it got stolen because it was soooooo much better than the TI-89. For one thing, it had a dedicated fractions key! For another, the interface was a whole lot more intuitive for people who'd never used a graphing calculator before. And you could also edit equations after you input them and got an error instead of having to type them over from scratch.
Who wants to become a writer? And why? Because it’s the answer to everything. It’s the streaming reason for living. To note, to pin down, to build up, to create, to be astonished at nothing, to cherish the oddities, to let nothing go down the drain, to make something, to make a great flower out of life, even if it’s a cactus. — Enid Bagnold
