Shell script keeps me happy, you've not lived until you've used join(1) in production. http://man.cat-v.org/plan_9/1/join
Assembler is good especially on something clean like a microcontroller. I like the AVR instruction set. http://www.maht0x0r.net/library/computing/avr/docs/8bit_avr_...
Hook up an AVR to a GSM module and a SIM and you've got you're own programmable cell phone, like this one http://www.sparkfun.com/commerce/product_info.php?products_i...