"The Flower of the Trees" That's the name of the Gothic poem that Tolkien composed. It's got the alliteration traditional for old Germanic poetry (even though this was composed in 1936), and personally I really do like how it sounds (this page, despite a couple of typos, has .wav files so you can hear it).
To show you a bit of the fun I get from comparative philology, I just wanted to point out how many cognates this poem shares with modern English. Out of 55 words, here are 32 cognates for 34 words (2 appear twice) or 62% of the words in the poem. And this is just what occured to me on first glance (at 1am). The Gothic words below don't all do exactly the same job their English cousins do, but they're in the same field usually. Starring, in order of appearance, are:
bairiþ: bears ("beareth")
gilwa-groni: pale green ("yellow-green")
bagme: trees ("beam")
bloma: flower ("bloom")
fagra-fahsa: fair-haired ("fair" & "faxen", whence "Fairfax")
fairguni: mountain ("-berg")
Wopjand: calling ("weeping")
wagjand: shaking, moving ("wagging")
slaihta: smooth ("slight")
raihta: straight ("right")
hweita-rinda: white-barked ("white" & "rind")
runa: mystery, secret ("rune")
þiuda: people ("Theoden", "Deutsch" [ok so this isn't English])
Anda-nahti: evening ("night")
liuhteiþ: lights ("lighteth")
lausai: free ("loose")
triggwa: faithful ("true")
beidiþ: awaits ("bideth")
Some generalities to note in comparison:
In OE, the 'ai' or 'a' of Gothic often became 'æ', as in OE bær (from beran) for Go. bar (from bairan).
After vowels, the 'g' in OE tended to be pronounced like our 'y', so that "fair" was spelled fæger, but pronounced close to our own word. Gothic, however, pronounced the 'g' in fagr.
The OE 'g' also sounded like a 'y' in front of "front vowels" (æ, e, i, y). Hence gear > year; geard > yard; and, above, Go. gilwa- beside OE geolu > yellow ... BUT ... hard 'g' sounds at the front of 'glittering' (Go. glitmunjandei, OE glæteriende) and 'good' (Go. goda, OE gód).
Baza to English bare is an example of s's becoming r's. This is called rhotacization, after the Greek letter.
Finally, isn't it just more fun to pronounce the gutturals in words like slight, right, light, night? My favorite line of the poem, for sheer enjoyment of hearing the sounds, is slaihta, raihta, hweitarinda. Smúúð.