I would just go with the volume sorted in descending order:
1 Bitcoin $14,923,705,720 $925.74 16,120,787 BTC $86,743,200 2.03% sparkline
2 Ethereum $950,260,548 $10.78 88,177,322 ETH $7,289,660 0.95% sparkline
4 Litecoin $189,925,010 $3.84 49,466,981 LTC $2,427,200 -0.11% sparkline
7 Dash $107,532,214 $15.26 7,045,887 DASH $1,844,320 0.40% sparkline
5 Monero $168,796,832 $12.23 13,807,060 XMR $1,817,870 2.49% sparkline
28 E-Dinar Coin $8,293,219 $0.608827 13,621,634 EDR $1,595,990 9.82% sparkline
22 Tether $14,951,740 $1.00 14,951,591 USDT * $1,426,540 -0.00% sparkline
13 Factom $29,113,644 $3.33 8,753,219 FCT * $1,157,920 10.29% sparkline
6 Ethereum Classic $121,955,844 $1.38 88,138,763 ETC $825,106 0.44% sparkline
16 Zcash $21,795,697 $43.18 504,781 ZEC $772,752 -1.26% sparkline
https://coinmarketcap.com/They are the top 10 in my opinion, and interestingly, not all of them are in top 10 by market cap.
Zcash Coin must be interesting, and also Tether which is a very classic old coin.