pepsi
pens
pencils
prams
packs
parks
presents
peace
people
parks
In hiragana I only know of PACHINKO and the onomatopeic ぺらぺら (fluent, talkative). In katakan there are many many more (specially for food).
There are many japanese cartoon characters starting with the letter p, one example is: Piophonikato
Pessimistic is a synonym for something bad happening. It begins with p.
pentagram
Pulses
peso
Mikasa
Pants
pineapple juice
Distance
phobia
pne
· South China Sea · Sea of Japan
Pop, pineapple juice, pomegranate juice
phobia
Pet bird.
Frying Pan
personification, peas, please, poncho, pontoon boat, panda
Pretty Perfect Pure Passionate Petite :)