I seem to remember getting a barton 2400+ with a 9700 pro. Damn was I excited. That was awesome.
I can't say what is best and worst, but my two favorties were my Athlon 64 FX-57 and then E8400, then 2600k....actually screw it. All my rigs have been BOSS. Never purchased a crappy CPU.
Yeah I remember getting the Barton 2400 overclocking to 3200 speeds and buying some variant of Radeon 9500 where you could flash it and it performed similar to the much pricier 9700.
My best CPU was Celeron 300A, just changed a jumper on motherboard from 66mhz to 100mhz and you had near or better than P2 450 performance for a quarter of the price.
P4 Northwood 2.4C @ 3.4 ghz was also a good cpu for me.
Q6600 (G0 SLACR) @ 3.8 ghz, bought it 6 years ago, not my main desktop (guests who come over will use this computer) but it still runs like a champ.
My main rig is an i7 2600K @ 4.5 ghz that I bought around 16 months ago and I'm really happy with it.