Yeah, I am a KSP nut too.
I don't do missions - I prefer making whacky things and making them work. The new flight dynamics to the latest update makes it quite realistic and the aircraft are more flyable.
My favourite thing to do is skimming - hitting the atmosphere at an alarming rate and keeping it in the skim, then creating a stable symettrical orbit. Or the other favourite is making hypersonic craft, vertically. If Idon't get the shock clouds and vortices before 800m I have failed

(just use a probe with either the small solid propellant pack or multiple of the tiny solid tubes - light and fast)
Such an enjoyable, simple game. I often like landing an aircraft or pod somewhere odd and getting Jebediah out for a walk...