I'm not going to say anything, I'd rather my favorite parts didn't get any more expensive!
I flipped a bike with those challenge derailleurs. You're right; they work great.
I'll try to think of others...
Deore DX - it looks great, it's durable and you can find it inexpensively on parts bikes.
Most underrated components?
● 1971 Grandis SL ● 1972 Lambert Grand Prix ● 1972 Raleigh Super Course ● 1972 Peugeot UE-18 Mixte ● 1980 Apollo Prestige fixie ● 1982 Motobecane Jubile Sport ● 1983 Nishiki Landau ● 1984 Peugeot PH10LE ● 1984 Bianchi Limited ● 1985 Peugeot Vagabond ● 1985 Trek 600 ● 1985 Shogun Prairie Breaker ● 1985 Raleigh Elkhorn ● 1986 Univega Nuovo Sport ● 1987 Schwinn Tempo ● 1996 Kona Lava Dome ● And a Bike to Be Named Later ●
Another vote for Deore DX 95% of XT, 25% of the price.
The mid-1980 Shimano Z-series. Reasonably priced, nicely finished, works very well, bullet proof.
Old Falcon branded triple front derailleurs. Work fantastic, and you could probably get them at 10 for a buck.
"Where you come from is gone;
where you are headed weren't never there;
and where you are ain't no good unless you can get away from it."
I'd vote for Araya steel rims, if you can find a perfect set.
I believe that these are the smoothest I've ever used in terms of braking, and not too terribly heavy.
Not the MOST underrated, but I have a fetish for Lyotard pedals. They're not smooth, but they are quite durable. There's only one model I know of with a design flaw. It has an aluminum shaft around the spindle. But I don't have that model. I'm hoarding all the Lyotard rat trap pedals I can find. I don't even know why.
I'm finding that a lot of the stuff I like is well regarded and priced accordingly.
*Recipient of the 2006 Time Magazine "Man Of The Year" Award*
Anything tubular and freewheel in the same wheel. Hubs are worth 95% of the whole wheel if they are C-Record , Mavic 501, almost any freewheel wheelset for that matter. Specialized Flag CS's, last generation of Tricolor single pivot brakes , great performance from a single pivot with the tricolor levers. Suntour XC comp brakes and CS's. Winner branded hubs.
Simplex Prestige derailleurs. Perform well for me. Victim of cycling myth.
Shimano 1050 6-sp indexed. Light, capable, cheap, and polished.
Perhaps you didn't really hear what you thought I said...
...or maybe you did, and that's why you're so mad.
1982 Lotus Classique
1986 De Rosa Professional SLX
1987 D'Arienzo (Basso) SLX
1995 Hot Tubes TT
1998 Kestrel KM 40 Airfoil
2006 Cinelli XLR8R-2
2011 Eddy Merckx EMX3
2014 Wraith Hustle
Mavic 500's are underrated but have a following. I thought they would be easy to find because they are not mentioned that much. Boy howdie did I get a surprize when I did find them. Typically they are priced the same as Campy HF hubs or more. Try to find skewers! Ha!
French bikes because of their non standard dimensions.
Suntour XCD - I have a couple 6000 rear derailleurs and they have been flawless for me.
1975 Motobecane Le Champion
1984 Bridgestone 400 -- 1985 Specialized Expedition 1986 Cannondale ST400 and Nishiki Cascade -- 1987 Trek Elance 400T and Schwinn Voyageur
1990 Cannondale ST400 -- 1994 Univega Via Carisma
For C&V, old Weinmann brake levers - cheeeeeeap prices, lightweight and they work. Comical of the market value difference vs. old Mafac (and those crazy prices for Mafac hoods...whew!).