Seems like there's two questions here 1. for a plane (I presume carry on) which means it has to look benign.
2. something more scary looking- which opens up a field of bezelled possibilities.
Re 1. the easy to find cheap choice is the lowly mini maglite (2xAA or 2XAAA), preferably brightly coloured rather than tactical black- looks unassuming. Not very bright, for the cheapest you don't even have to get an LED version- which makes it almost disposable.
Though I also carry a blue Streamlight Stylus Pro 2xAAA on planes:http://www.streamlight.com/product/product.aspx?pid=133
Another cheap black flashlight in the Fenix series I like is the E21 (2xAA), but I wouldn't take it on a plane:http://www.fenixlight.com/viewnproduct.asp?id=72
The good thing is it's cheap, sturdy, and uncomplicated- has only two settings to worry about- superbright, and actually able to be used to read something. I think some of the lights with 5+ output settings are a pain in the arse. Often times uncomplicated is the way to go.