What would I use on a daily basis in college, and enjoy doing so?
The HP 15C was my answer.
First made from 1982-1989 and then released as a limited edition in 2011, with only 10,000 made, this scientific calculator was a standard for scientists and engineers everywhere. It's a cousin of the famous HP 12C financial calculator, which my dad happens to use almost daily.
RPN: 2 [enter] 3 [x]
Algebraic (normal) input: 2 [x] 3 [=] 6
This is advantageous because it affords fewer keystrokes, 4 vs. 5. The advantage is even more apparent when looking at more complex calculations.
RPN: 2 [enter] 3 [+] 5 [enter] 1 [-] [x]
Algebraic: [(] 2 [+] 3 [)] [x] [(] 5 [-] 1 [)] [=]
9 vs. 12 keystrokes.
And it's just more fun to use!
This calculator can do numeric integration, complex calculations, matrix algebra, equation solving, and can execute programs. Overall a fun and useful tool.