teemo is not a solo mid, unless that is a new meta for pre-lvl 30's. but i would say wait for 3150 ip for kass, anivia, or karthus which are all better heros in general oppose to veigar and teemo.
if you really can't wait i would say morg or zilean. those 2 are very op. morg ult can dominate a fight,
or zil ult can bait 4-5 of their ults just to have them revive with a GA eff with massive utility.
If neither of those sound good i say get singed for trolololololololololololololololololololololololol ololololololololololololololololololololololololol ololololololololololololololololololololololololol ololololololololololololololololololololololololol olololololololololololololing
or jax because he is fun