Things I like (about)

Asterisk

• Consistency in design of various subsystems.
• Extensible design.
• Multiple ways to modify and reprogram it without changing a single line of code.
• Open source.

Python

• Very compact syntax (quick to learn, hard to forget).
• No superfluous built in commands or syntax.
• No need to compile.
• Commonly used high level data structures are built into the language.
• Programming can be done extremely quickly (and it just seems to work).

C

• High level enough to get things done.
• Close enough to the machine level to write device drivers and build efficient applications.

Open Source.

• Community.
• It seems with open source the market comes to you instead of the other way around. (I.e. you're not marketing a product. Others will find your software if it's useful.)
• It works. And if it doesn't you can fix it.
• You can learn from it.