Hardly would I recommend some other investment besides Bitcoin, but if you can afford to take bigger risks, you can play with some altcoins, not putting too much money into it, of course.
I agree that bitcoin is very safe and sound for any average investor in trading. The current price fluctuations in bitcoin make it a good source of income for the traders and hence its recommended before any other altcoin. Altcoin trading is there but its risky and not recommended. If you know some altcoin is not going to turn scam you are free to invest in it, but there have been many cases of altcoins being pump and dump schemes and pure MLM schemes. So we must be careful about investing in altcoin trading.