Based on Japanesepod101′s videos, here is a helpful list of memory aids for all the Japanese katakana characters / symbols:
ア a – looks like an Axe
イ i – looks like i-sel / easel
ウ u – looks like an angular-connected version of hiragana u う (like a beret hat – bu-ret?) U+” = Vu
エ e – elevator doors
オ o – opera singer
カ ka – looks like hiragana ka か but more angular
キ ki – looks like hiragana ki き without bottom bit
ク ku – kuku’s tail (cookoo bird tail)
ケ ke – like a sideways K (it can be seen as a T but if you think “I don’t recognise this T.. what T sound is this?” think – ahh it must be ke!)
コ ko – korner / corner
サ sa – saddle
シ shi – SInking SHIp smiley
ス su – su-kiing figure (like a figure skiing) like a gimmel
セ se – looks like hiragana se せ (eg sensei)
ソ so – smiley with one eye (looks like n [ン], but “so” [ソ] is “s”limmer. It also looks like a SOftserve ice cream and “n” does not.
タ ta – person holding a tablet
チ chi – chicken that looks nothing like a chicken 
– chi looks like an energetic (chi-filled) man with spread out arms and looking upwards, running. [similar to ki キ.. if it's not ki, it's chi チ - Chi looks more like it's in the T series coz if its T-shape]
ツ tsu – smiley – like a smiling Tsu-na (tuna) face – looks like “shi” but if you trace the lines into curves, it shows the hiragana hint for which is which: つ or し
テ Te – telephone pole
ト To – totem pole side
ナ na – na-if (knife) or sword with cross at top
ニ ni – like 2 lines ni = 2
ヌ nu – like nu / noo / noose
ネ ne – nest
ノ no – no sign crossing out
ハ ha – ha-us – house
ヒ hi – heel (like a small t – a small tea is what women in heels drink)
フ hu or fu – tip of a foot “foo” – looks like a u on its side
ヘ he – looks like hiragana he へ
ホ ho – holy cross, shining
マ ma – mantaray wing
ミ mi – middle – 3 lines with a middle one
ム mu – mu-se – moose antlers
メ me – me-il – mail letter
モ mo – looks like hiragana mo も
ラ ra – rack or ra-cking chair
リ ri – looks like hiragana ri (not the print one: り but the other, handwritten one: ㇼ )
ル ru – looks like a ru-t root of a tree
レ re – Re-zor blade Edge / razor, or Edge of Rectangle
ロ ro – robot mouth square
ヤ ya – looks like hiragana ya や only more angular
ユ yu – looks like a U-boat’s periscope (or like a bet) – or like a sideways U
ヨ yo – looks like a backwards E – if you have an Egg, it contains a YOke. E for egg YOlk.
ワ Wa – like a Wain / wine glass
ヲ Wo – like wain glass but with extra line – like a world trophy or olympic torch
(ヰ wi)
(ヱ we)
ン n – smiley with one eye – or like space craft ENtering the earth’s atmosphere. Looks similar to “so” (but “so” is Slimmer)