just one? I'm assuming it is to be ridden & not put in a museum, so...
well, the Vincent is nice, but you'd need a ton of $$$ for parts/upkeep; the Manx Norton too, but only if you raced it - really impractical on the road. I too like BMWs (wish I had a GS1200 for where I live - lots of dirt roads & mild offroading - rather than a RT1100 - which finances & a new(ish) bike - the Savage - encourages me to sell). Surprised nobody chose the BSA 500 Goldstar single - an old "hot" single you could use on the road.
I'd like the 1980 Yamaha SR500 single roadbike I had back - the 1961 BSA 650 Super Rocket too!
A 1969 Triumph Bonneville (arguably the best year/looking one) would also be nice, though after reading up on Bonnevilles seem they always had trouble right up until they stopped making them years later (no, not Lucas electrics - never had trouble on the British bikes I had), though this sounds like the little bugs (yes, I've - still - got the oil leak - getting round to it once I have the courage up).
Actually, I like the Savage - with better brakes (I've upgraded), better forks (I'm happy with stock & a Superbrace), belt drive (hey, what do you know!?), better than stock tires (could not afford Metzlers so have got Dunlops), better rear suspension (saving up), lower bars (swapped out) & no oil leak (like I said...) & last not cruiser style (why I'd like the SR500 back), but you can't have it all...
I only ever saw one Savage before I saw my one - years ago - & said I'd really like one (ie a new large not offroad/enduro single) - if I ever saw one for sale @ a good price. I did!
So - maybe the Savage is my dream bike - small, light, enough power (I don't need to race along an Interstate) & able to whip through the bends with lots'o'torque.
I know it makes me do this

everytime I ride it!
george