Poll: Do you customize the TCP/IP settings of your OS, Router or Firewall?

I am curious how many people customize settings such as initial window size, window scaling, TTL, SACK, MSS, memory allocation, syn retries, synack retries and such.

If yes, please describe some of the things you tune, tweak, modify or otherwise adjust if you are willing to share. I won't pick apart the answers, there is no wrong answer. If someone does respond please be polite when asking them about their choices.