I had a budget of about $400 plus a pile of nice parts. I wanted a bike for short track XC racing. Here's what I came up with.
1999 Kona Muni Mula
Avid Speed Dial SL levers
Deore M590 shifters
Deore XT front derailleur
Deore XT rear derailleur
Deore XT crankset
Avid Single Digit 5 brakes
Ritchey Comp bar
Lizard Skins grips
Specialized Phenom saddle
Continental Speed King 2.3 tires
Mavic X221 rims
Deore LX M570 rear hub
Kona front hub
Interloc seat post
25.6 pounds
The stock parts that I got with the bike weren't bad (older XT/LX mix), but I was able to shave a couple of pounds off the bike just installing the parts I already had from a bike that I had over-upgraded a couple of years ago.