This list is intended to help you prioritize 100 very important words to learn in Old English, but you'll certainly need to go beyond it to get a good understanding of Old English.

Abbreviations

Abbreviations used here: 1st per. - first person; 2nd per. - second person; 3rd per. - 3rd person; acc. - accusative; art. - article; av. - adverb; conj. - conjunction; dat. - dative; dem. - demonstrative; fem. - feminine; gen. - gentive; hv. - helping verb; imp. - imperative; ind. - indicative; lv. - linking verb; masc. - masculine; neut. - neuter; nom. - nominative; pl. - plural; prep. - prepositionl; pres. - present; pron. - pronoun; pt. - participle; sg. - singular; subj. - subjunctive; vi. - intransitive verb; vt. - transitive verb.

List

Note that the numbers of this numbered list do not signify any kind of priority over other words in the list; rather they help to keep track of how many words there are and make sure there are only 100.

1. cuman sIV - to come
2. dōn (pres. ind.: 1st per. dō; 2nd per. dēst; 3rd per. dēþ; pl. dōþ; pres. sub.: sg. dō; pl. dōn; past ind.: sg. dyde; pl. dydon; past subj. formed off past ind. pl.; past pt.: dōn; pres. pt.: dōnde; imp.: sg. dō; pl. dōþ) - vt. to do, to make
3. for prep. +dat. - for, for the benefit of; because of
4. fram prep. +dat - out of, from; away from; by (person/agent)
5. gān (pres. ind.: 1st per. gā; 2nd per. gǣst; 3rd per. gǣþ; pl. gāþ; pres. sub.: sg. gā; pl. gān; past ind.: sg. ēode; pl. ēodon; past subj. formed off past ind. pl.; past pt.: gān; pres. pt.: gānde; imp.: sg. gā; pl. gāþ) - to go, to travel
6. ġē (acc. ēoƿiċ, ēoƿ; dat. ēoƿ; gen. ēoƿer) - you (plural), you guys, you all
7. ġit (acc. inċit, inċ; dat. inċ; gen. inċer) - you two, you both
8. hē (acc. hine; dat. him; gen. his) - he
9. hēo (acc. hīe; dat. and gen. hire) - she
10. hēr - av. here, at this place
11. hider - av. here, hither, to this place
12. hit (acc. hit; dat. him; gen. his) - it
13. hƿā (acc. hƿone; dat. hƿǣm, hƿām; gen. hƿæs) - who?
14. hƿæt (acc. hƿæt; dat. hƿǣm, hƿām; gen. hƿæs) - what?
15. hƿider - av. where?, whither?, to what place?
16. iċ (acc. meċ, mē; dat. mē; gen. mīn) - I
17. macian w2 - to make
18. man pron. (used usually only in nominative) - one, "you", someone (as in "one/you might say")
19. nāht pron. (acc. nāht; dat. nāhte; gen. nāhtes) - nothing
20. nā/nō av. - never, (emphatic) not (when used with verbs); not (when used with adjectives)
21. ne av. - not (used with verbs only) (comes before the verb in Old English, unlike in Modern English - so "Iċ ne cume" - "I am not coming", and not "Iċ cume ne")
22. oþ prep. +acc. - up to, until, so far as (of time or space)
23. se (masc.: nom. se; acc. þone; dat. þǣm, þām; gen. þæs; neuter: nom and acc. þæt; dat. þǣm, þām; gen. þæs; feminine: nom. sēo; acc. þā: gen. and dat. þǣre; plural all genders: nom. and acc. þā; dat. þǣm, þām; gen. þāra) - art. the; dem. that; pron. that (one)
24. seċġan (pres. ind.: 1st per. seċġe; 2nd per. sæġst, sagast; 3rd per. sæġþ, sagaþ; pl. seċġaþ; pres. sub.: sg. seċġe; pl. seċġen; past ind.: sg. sæġde, sagode; pl. sæġdon, sagodon; past subj. formed off past ind. pl.; past pt.: sæġd; pres. pt.: seċġende; imp.: sg. saga; pl. sagaþ) w3 - vt. to say, to tell
25. tō prep. +dat. - to, towards
26. þanne/þonne - av. then, at that time, during that time; conj. when, during which time; than (in comparative clauses)
27. þǣr - av. there, at that place; then, at that time; conj. when, at which time
28. þider - av. - there, thither, to that place
29. þes (masculine: nom.. þes; acc. þisne; dat. þissum; gen. þisses; neut.: nom. and acc. þis; dat. þissum; gen. þisses; fem.: nom. þēos; acc. þās; dat. and gen. þisre, þisse; pl. all genders: nom. and acc. þās; dat. þissum; gen. þisra) - dem. this; pron. this (one)
30. þū (acc. þeċ, þē; dat. þē; gen. þīn) - you (talking to only one person), thou
31. ƿē (acc. ūsiċ, ūs; dat. ūs; gen. ūre) - we
32. ƿeorðan sIIIc - lv. to become, to turn into
33. ƿesan/bēon (pres. ind.: 1st per. eom, bēo, bēom; 2nd per. eart, bist; 3rd per. is, biþ; pl. sind, sindon, bēoþ; pres. sub.: sg. sīe, bēo; pl. sīen, bēon; past ind.: sg. ƿæs; pl. ƿǣron; past subj. formed off past ind. pl.; past pt.: bēon (only ever used once - use usually instead past pt. of "ƿeorðan" or simple past of "ƿesan"); pres. pt.: ƿesende, bēonde; imp.: sg. ƿes, bēo; pl. ƿesaþ, bēoþ) (note that the "bēon" forms can actually have an explicitly future sense) - lv. to be; vi. to exist
34. ƿillan (pres. ind.: 1st per. ƿille; 2nd per. ƿilt; 3rd per. ƿile; pl. ƿillaþ; pres. sub.: sg. ƿille; pl. ƿillen; past ind.: sg. ƿolde; pl. ƿoldon; past subj. formed off past ind. pl.; past pt. not recorded to ahve existed; pres. ƿillende; imp. forms not recorded to have existed) - hv. to want, to desire (note that this verb never takes a nominal object)
35. ƿit (acc. uncit, unc; dat. unc; gen. uncer) - we two, we both