45mm is a very unique focal length that you don't see often. It's almost perfectly matched to the diagonal of 35mm film making this more of a "normal" lens than the eponymous 50mm is. It helps that the lens is absolutely amazingly sharp even on extremely high resolution digital cameras. The odd focal length makes the lens less popular than it really deserves making it cheaper than its 50mm stablemates in the SR mount. If you don't need a lens faster than f/2 I strongly recommend taking a look at this one. I bought mine from eBay for about $30.
Minolta MD Rokkor-X 50mm f/1.7
Quality performance in a small lens and affordable price.
Minolta MC Celtic 135mm f/2.8
A great portraiture lens with a bright aperture.
Tamron Multi/C 80-205mm f/3.8
A faster than average portrait zoom
Minolta MC Rokkor-PF 58mm f/1.4
A robust classic with fantastic rendering and rock solid build.
Minolta MD Celtic 28mm f/2.8
Extremely lightweight wide angle with good center performance.