These mostly come from the reconstructions provided in Wright's Grammar of the Gothic Language, available online as .png files.
I may have made some errors in my transcriptions. Please email any corrections to kesuari at yahoo.com.au. At this stage, very little background information is provided. If you want some, take a look at Wright's Grammar.
Obviously, anything from Proto-Germanic is a reconstruction, but for conciseness, I've generally skipped the traditional asterisk. The yogh and dashed-b from the Grammar are transcribed here as *g and *b, but macrons are still used above long vowels, so a unicode font and recent browser are necessary.
Note that though Proto-Germanic may have had an instrumental case, it is not shown in Gothic and so I only have it for one declension (masc. ja-stems). Further information is welcome!
Note that Peter Petersson's page on the Old Norse Language has some information on Proto-Germanic, but as it's not his primary concern, it's poorly formatted. My tables are different from his, I think, so one of us may be wrong. Or Old Norse may have taken the instrumental in some cases, which I mostly lack...
In most other Indo-European languages, these are called o-stems, but IE *o became Proto-Germanic *a, and so the name changed with them. This class consists of masculine and neuter nouns. In addition to pure a-stems, there are ja-stems and wa-stems.
|Nom, acc, dat||-an||worðan2||-ō||worðō|
|Nom, acc, voc||-jan||kunjan||-jō||kunjō|
(When I work out the wa-stems, they'll go about here. I imagine they're much the same as the ja-stems, though.)
These are all feminine nouns, and also have jō- and wō-stems. I don't know anything about the wō stems (though I imagine it's mostly a case of prefixing the pure ō-stem inflexion with w-), but in with jō-stems, the major differences are that the nominative singular is *-ī (e.g. *bandī) and the other cases and numbers simply prefix the inflexion with -j- (e.g. nom. sing. *bandjōz).
These were both masculine and feminine, and were the same in both genders.
There were masculine, feminine and neuter u-stems. I'm not sure whether the neuter nouns were decined the same as the masculine and feminine nouns or not, but I'm pretty sure those two were. However, as we begin to have a less-strong declension, my confidence in what I have decreases. Unfortunately, that pun continues... From Wright's Grammar, all I can say of the neuters is that the nominative and accusative (plural?) ended in *-u. More information would be appreciated.
Either I got tired while reading my sources, or my sources were skimpy on this. At any rate, being weak declensions, my knowledge of them is weak, too (there, I told you, but I'll drop it henceforth). These are also known as consonant-stems, because whereas the strong declensions had vowels as their stem, these ones get a lowly consonant.
One thing to note is that Wright's Grammar has a tilde above some of the vowels (e.g. 'In the parent language [i.e. Proto-Indo-European, but also in Proto-Germanic (mentioned later)], the nom. sing. ended partly in -ēn, -ōn and partly in -[e-macron-tilde], -[o-macron-tilde]'). This confuses me. I'm not sure how to deal with it, and it doesn't help that I can't rely on the Unicode combining diacritics because sometimes they don't. Did IE have nasalised vowels? This is all I've heard of that. I had heard of nasalised vowels in Proto-Germanic, but they appeared to have come from the loss of nasal consonants. The different Germanic languages, at any rate, dealt with the *-n and *[tilde] forms in different ways: Gothic generalised the *[tilde] to feminine and neuter, but West Germanic generalised it to the masculine. Old Norse appears to have made a bunch more categories from this one, so I don't know what it did.
|Nominative||-ō(n) (but see above)||hanōn||-aniz||hananiz|
|Accusative||-anum||hananum||-(a)nunz||hananuz < hannunz|
|Genitive||-enaz, iniz||hanenaz, haniniz||-nōn||hannōn|
|Nom, acc.||-ō (but see above)||hertō||-ōnō||hertōnō|
|Genitive||-enaz, iniz||hertenaz, heriniz||-nōn||hertnōn|
R-stems are a bit trickier. Incidentally, these, along with the -nd-stems which are the most confusing, kept the root-vowel into modern English, whereas the other classes lost them. The tricky thing about these ones is that we have an alternation between *-e- and *-a-. Looks like an ablaut that never settled down. Another interesting note here is that the Proto-Germanic words for father, mother, daughter, brother and sister were all a member of this class. 'Father', 'mother' and 'daughter' were all content to use the *-e-forms. 'Sister' was content to use the *-a-form. But we know how brothers can be...
|Nominative||-ōr, -ēr (but see above)||broþōr||-ariz, -iriz||broþariz|
That's all for now, folks. I'm not sure of how the -nd-stems work, and adjectives and verbs are a story for a different day.