B1V

Garrison96 does not list a B1V dagger, but ome^1 Sco would be a good dagger

HD 144470 = Ome^1 Sco is probably the best standard

Lesh68, Hiltner69, Walborn71, Garrison77, Garrison79 & Walborn90 adopts Ome^1 Sco
as their B1V standard

Garcia89 lists 4 B1V MK standards: HD 7252, 24131, 37018, & 144470

MK43 listed Eta Ori as their B1V MK standard. 

Skiff08 lists two B1V standards: HD 37018 (MK73) & HD 144470 (MK78).

Median Mermilliod91 colors among the standards:
<B-V>(B1V) = -0.256 (N=4 standards)
<U-B>(B1V) = -0.955 (N=4 standards)

# Primary Standard
HD 144470 = ome^1 Sco = HR 5993
  B1V: JM53,Hiltner69(stan),Walborn71,MK73,Garrison77(stan),MK78,Houk,Keenan85,Walborn90,GrayAtlas
  M91: V=3.954+-0.012, B-V=-0.041+-0.007, U-B=-0.823+-0.005
  =>QBV=> (B-V)o=-0.256, (U-B)o=-0.954, E(B-V)= 0.215, T=25822.

# Other Standards
HD 7252 = ALS 6493 = MCW 58
  B1V: JM53,Morgan55,Hiltner56,Fehrenback60,Jaschek64(all),Jensen81,Garcia89
  B2III: Bartaya83
  B3: Cannon
  Good agreement on B1V, but no published Teffs
  M91: V=7.129+-0.011, B-V=0.075+-0.019, U-B=-0.740+-?
  =>QBV=> (B-V)o=-0.256, (U-B)o=-0.955, E(B-V)= 0.331, T=25845.

HD 24131 = HR 1191 = MCW 251
  B1V: JM53,Morgan53,Morgan55,Underhill57,Jaschek64(all),Jaschek78(JM53),Garcia89
  B0.5V: Hiltner56,Lesh68
  B3: Cannon
  M91: Vmag=5.772+-0.011, B-V=-0.004+-0.012, U-B=-0.796+-0.015
  =>QBV=> (B-V)o=-0.256, (U-B)o=-0.954, E(B-V)= 0.252, T=25807.
  
HD 37018 = 42 Ori = HR 1892
  B1V: Lesh68,MK73,Abt77,Garcia89,Houk(from Garrison)
  B2III: Jaschek78,Morgan55
  B2: Beer61,Sharpless52
  B3: Cannon
  Jaschek64 split between B2III and B2IV
  Fairly good agreement on B1V
  Reed05: V=4.59, B-V=-0.20, U-B=-0.94
  =>QBV=> (B-V)o=-0.257, (U-B)o=-0.957, E(B-V)= 0.057, T=25934.

# Weak standard
HD 35411 = eta Ori  
  B1V: MK43,Wood55,Sharpless52
  B1IV: Abt77
  B1: Cannon
  B0.5Vnn: Morgan55,Lesh68
  B0.5IVk: Buscombe69
  B1V+B2: Levato75
  Jaschek64: mostly B1V with few B0.5V 
  Algol variable and 1.5" resolved pair
  Was "the" B1V standard in MK43, but it later changed in the literature. 
  Probably a poor choice of standard

# Others

Alf Cru B
  B1Vn: Garrison96

Alf Vir
  B1V: Garrison96