1-Harp. Simple yet elegant. A harp says you are cultured and classy. A harp also says you are a caring, gentle soul (ladies ;) )Also, you will look like an angel. Be sure to point out that your instrument has 46 strings compared only six strings. That makes your instrument 7.666 times harder to play. The women will be turned on by your math skills.
3-Organ. People will be impress purely that your were able to bring an organ to the party. You only need to be able to play a song or two to impress people.
4-Keytar. Excuse me how many instruments does your instrument combine? Yeah that's what I thought. Keytars used to popular so I am sure they are making a come back, probably. You will look like your own man because no one gives keytar lessons so you have to teach yourself. Imagine this conversation:
Hot girl: So where did you learn to play keytar?
You: I had to teach myself. No one gives lessons. If you don't believe me you can check craigslist.
Hot girl leaves
Hot girl returns 2 minutes later
Hot girl: I just checked craigslist. You were right. That is hot.
Hot make out session