Favorite calculator: the HP 50G!
The most powerful calculator, ever.
Instantly let you know, "it's pro." Feels great in your hand. The keys have a very satisfying tactile "click" (unlike the 49G, which had cheesy keys). It can do everything the wonderful HP 48, in all its varied forms, can do (over 2300 built-in functions+any you wish to add), great equation libraries and many, many constants predefined, PLUS does graphics, has much greater capacity both internally (2.5 MB) and externally (with swappable SD cards holding gigabytes of programs and data each--you'll never run out of room), and it has a USB port, a serial port, and an infrared port. Has HP Solve (plug in what you know, solve for any variable) and Computer Algebra System (CAS)--both very good. Redefineable keyboard and menu keys. RPN is awesome! But if you're not sure whether that's your bag, it's switchable between RPN, algebraic, and "textbook" modes--your choice. You can change all sorts of flags to customize everything to work exactly how you want it to. Comes with connectivity software to hook up your computer--easy to load programs (lots of games, too). With available ROMs you can upgrade it to take advantage of future improvements. You can write software for it on your desktop, if you're into that, test it on the free emulator (looks and works exactly the same as the real calc), and then load it up. Or you can program right on the calculator, if that's your thing. You can program it in C (using HPGCC), User RPL, System RPL, HP Basic, Saturn Assembly, and ARM Assembly. Best of all, it can be had for $85 new and in the sealed packaging on eBay (nearly half the retail price). BTW, the old HP 48 progs can be converted to run on the HP 50 with a free utility (HP 49G programs run on it natively). I've used mine every day at school for a month, and only just now replaced the AAA alkaline batteries. (Thinking of switching to rechargeable Li-ion.) Scientific functions, statistical, financial, logic, unit conversions, matrices, algebra, trig, systems of equations, integral and differential calculus, you name it. Or customize with all your own stuff. Plays Wolfenstein, Dune, Pac-Man, Tetris, and other games for when you're bored, and you can use it as a TV remote. What more could you want? Oh yeah--snazzy leather(-ette?) case. Accept no substitutions!
--Mike from Shreveport