i agree with Epix...tremble clef. lolz. pretty funny. i would suggest piano, ive always wanted to play the piano, just never got a chance to do it. Also, playing the piano seems to help a lot with as someone already said multi-tasking, and reading treble clef, as well as music theory. Knowing music theory will basically help you in everything and help you in all endeavors with instruments, no matter which one you may later decide to play.

oh yeah, and i also recommend to not give up the violin after one or two years. i sucked at it after one year(people used to make fun of me and stuff for being so junk), but they key is to never give up. You definetely will get better over time, as long as you practice. Practice is also key when learning any instrument.

maybe piano, but its a lot harder to go from violin to piano, than piano to violin... for many reasons, i wont bother listing them

I was a string player first, but I ended up picking up clarinet, and I love it. I`m now a professional clarinet player. Try a woodwind, it`s totally different and you may like it!

As for difficulty in playing;

String instruments:

violin and viola are slightly harder than `cello and bass.

Woodwinds:

oboe and bassoon are harder than clarinet and flute

Brass;

horns are much more difficult than the other brass ( trumpets, trombones and tubas )

All instruments are difficult to some degree though.

I thought it was easy to go from violin to piano (?) I don`t know why, but it`s so simple to make a good sound, and the only things you have to worry about are learning to read the bass cleft and using your hands and fingers in a different way (if that makes sense). There`s no squeeking and bad intonation.