Will's vocabulary is growing too quickly for me to keep track, but one thing he is really into lately is singing. Until recently it has been too much for him to apply the words he learns to the songs he likes to sing. For example, he likes Take Me Out to the Ballgame, but can only sing the "one-two-three" [strikes your out] part, and otherwise just sings "ball" over and over. Also, he likes "Twinkle, Twinkle, Little Star", but only sings the final word of each line, the rest is too fast.
As his vocabulary grows, he can sing more and more of his favorite songs, which he will request we sing with him (more like demand we sing with him) at any time. The video below has him singing the Alphabet Song (which he calls "AyBeeCeeDees"), with just a little bit of help from dad (he has trouble with pronouncing "W" - which he calls a "Will"). Also note how he argues with me at the end of the song about who you should sing with next time - sometimes we go on for quite awhile with that part.
Will has been singing this song quite often lately. A lot of times when we put him down for bed or nap, we'll hear a few rounds of "ABCDs" before he finally drifts off. Sometimes he only wants Erin, or only I, to sing with him, and sometimes he demands a solo. Yesterday he demanded that we sing it together: "Wyall dada aybeeceedees". When Erin tried to sing along too, he stopped everything "NO NO! Wyall dada aybeeCEEDEES!!". Ouch, sorry mama. He says similar phrases so often sometimes he accidentally applies them to situations that don't fit. For example, I might try to help him get his socks on when he wants to do it himself - in his excitement he may yell "NO! WYall aybeeceedees!!!"