I had a TI nSpire CX CAS in high school (like the 89 but with a color LCD screen and hackable with Lua and C - it runs Doom and GBA/NES emulators). In the fina

I had a TI nSpire CX CAS in high school (like the 89 but with a color LCD screen and hackable with Lua and C - it runs Doom and GBA/NES emulators). In the final year of high school I was taking a class that did not require a graphing calculator, so I bought a TI 36X Pro, an advanced scientific calculator. It has excellent 'UI', tons of functionality, and the buttons feel great to type on (though after a long time they will still start to get mushy). I actually used to carry both of my calculators with me, the CAS for when I needed it and the 36X for normal usage since it felt better to use. It's not a school monopolozer like the 84/89 so it's priced well, at <$20. I bought another one in college after I lost the first one. I'm doing CS so I don't need it often, but I find it to be worth keeping around.