My recommendation would be the 105mm f/2.5. It's a legendary lens. Search the web and you'll find lots of information on it. The AIS version spends significant amounts of time on my FE2. (The built in sliding lens hood on th AIS version is very nice. I don't know if the newer AF versions have one or not.)

Since the lens has been made for so long, there are a ton of them available on the used market. Check KEH.com; they usually have a Bargain condition AIS for around $100-$110.