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the hope singlespeed hub always gets good praise.
this one is a novatec (D252SB-BO-AA )with aluminium everything so pretty light about 280-300g:
http://www.only-highend.biz/epages/63221174.sf/en_GB/?ObjectPath=/Shops/63221174/Products/OH-000065if you use a wide chainline (54mm, outer mtb crank chainring) the dmr revolver with normal freewheel is rock solid (steel axle, nuts, 76mm flange)
and can be flipped with a velosolo type 6 bolt cog on the other side (disc bracket has a chainline of 53-54mm)
Apart from budget, the main thing worth considering is if you want to use a screw-on freewheel, or a mini-cassette hub. I prefer the cassette type myself, as it's easier to get a perfect chainline and decent quality cogs can be bought quite cheaply.
Cheapset way is using a basic Shimano geared hub and a singlespeed conversion kit .