Since junior high school a calculator was a big part of learning mathematics especially when it came to algebra related tasks or anything else for that matter past the point of basic math schools. It has always been my weakest subject as well so a calculator has always been like a life line to me in that sense.
I started using Scientific calculators in high school and somehow managed to learn the basic functinality even though the devices still look alien to me.
When I entered college a Scientific calculator was no longer an option but a requirement and I definitely needed all the help I could get in that area if I wanted to get my degree.
I purchased the Texas Instruments T1-83 Plus model from the college book store on my first day of class as a Freshman and it hasn't let me down yet. I still have it after 6 years and it's still going strong.
One of the few things I DON'T like about this model is how bulky it is, but with so many functions I guess I can't expect it to be the size of my cell phone.
The battery life is wonderful given the size of this device as well and it's been beyond durable. I can't even count the times I've dropped the thing and all it has to show for it is some scratches on the case. It can't get better then that.
There are many newer models then the one I have now. Texas Instruments is always coming out with something better but for guaranteed quality and durability I recommend this one for the long haul.